GIFT  OF 


ORGANIC    CHEMISTRY 

INCLUDING  CERTAIN  PORTIONS  OF 

PHYSICAL  CHEMISTRY 


FOR 


MEDICAL,  PHARMACEUTICAL,  AND  BIOLOGICAL 
STUDENTS 

(WITH  PRACTICAL  EXERCISES) 


BY 


HOWARD  D.  HASKINS,  A.B.,  M.D. 

Professor  of  Biochemistry,  Medical  Department,    University  of  Oregon 

Formerly  Associate  Professor  of  Organic  Chemistry  and  Biochemistry, 

Medical  Department,  Western  Reserve  University 


THIRD  EDITION,   THOROUGHLY  REVISED 

TOTAL  ISSUE,  FIVE  THOUSAND 


NEW  YORK 

JOHN  WILEY  &  SONS,  INC. 

LONDON:   CHAPMAN  &  HALL,   LIMITED 

1917 


COPYRIGHT,  1907,  BY 
H.  D.  HASKINS 

AND 

J.  J.  R.  MACLEOD 


COPYRIGHT,  1917,  BY 
t\         HOWARD  D.  HASKINS 


PRESS  OP 

BRAUNWORTH  &  CO. 

BOOK  MANUFACTURERS 

BROOKLYN.    N.  Y. 


PREFACE  TO  .THIRD   EDITION 


IN  this  edition  the  subject  matter  has  been 
rearranged  to  a  considerable  extent.  Numerous 
revisions  have  been  made. 

The  discussion  of  the  physical  chemistry  topics 
has  been  amplified,  and,  hi  some  cases,  partly  re- 
written (e.g.,  osmotic  pressure  and  colloids). 

It  will  gratify  the  author  greatly  to  receive  for 
consideration  suggestions  and  criticisms  from  any 
who  are  using  this  text-book. 

HOWARD  D.  HASKINS. 

PORTLAND,  OREGON. 
Nov.  1,  1916. 

iii 


380850 


PREFACE  TO   SECOND  EDITION 


THE  author  has  endeavored  to  revise  the  entire 
book,  striving  to  make  it  more  reliable  as  a  reference 
book,  and  more  complete  from  the  standpoint  of  the 
student  of  medical  sciences.  It  is  our  belief  that  an 
organic  chemistry  text-book  for  the  use  of  medical 
students  should  give  the  chemistry  of  all  the  organic 
compounds  (of  any  importance)  that  enter  into  the 
study  of  physiology,  biochemistry,  and  pharma- 
cology. 

H.  D.  HASKINS. 

July  1,  1912. 

iy 


PREFACE  TO  FIRST  EDITION 


AMONG  the  most  important  of  the  recent  advances 
in  medical  science  are  those  relating  to  the  chemistry 
of  the  various  organic  substances  which  enter  into 
the  composition  of  animal  tissues  and  fluids,  and  to 
the  physico-chemical  laws  which  govern,  or  at  least 
influence,  many  physiological  processes.  The  dis- 
covery of  the  chemical  constitution  of  the  purin 
bodies,  of  many  of  the  urinary  constituents,  and  of 
sugars  and  fats,  as  well  as  the  new  theories  of  solu- 
tion and  catalysis,  has  revolutionized  the  teaching 
of  biological  and  clinical  chemistry;  and  in  phar- 
macology and  pharmacy  a  knowledge  of  organic 
and  physical  chemistry  is  almost  essential.  The 
study  of  these  parts  of  chemistry  is,  therefore,  daily 
coming  to  be  of  greater  importance  to  the  medical 
student  and  is  already  included  in  the  curriculum 
of  the  best  medical  schools.1 

As  taught  in  the  regular  college  classes  in  organic 
chemistry,  the  subject  certainly  absorbs  too  great  a 
proportion  of  the  medical  student's  time,  and  much 
is  included  in  the  course  which  has  no  bearing  on 

1  The  recent  application  by  Arrhenius  of  certain  physicochemical 
laws  in  explaining  the  mode  of  action  of  antitoxins,  etc.,  is  an 
illustration  of  the  increasing  importance  of  a  knowledge  of  physical 
chemistry  for  the  medical  student. 


Vi  PREFACE 

his  future  work,  and  much  is  omitted  which  is  of 
immense  importance  to  him. 

It  was  with  the  idea  of  presenting  in  the  simplest 
manner  the  facts  of  organic  and  physical  chemistry 
which  have  an  essential  bearing  on  medical  science 
that  the  present  book  was  written.  For  the  sake  of 
simplicity,  the  subject-matter  is  arranged  in  a  some- 
what different  manner  from  that  usually  followed  in 
text-books  for  chemical  students.  In  the  first  por- 
tion of  the  book  considerable  attention  is  given  to  a 
description  of  the  methods  employed  for  purifying 
and  testing  the  purity  of  substances  preparatory 
to  their  further  investigation.  It  is  to  this  part 
of  his  work  that  the  investigator  in  bio-chemistry 
has  to  give  his  closest  attention  and  in  which  he 
often  meets  with  the  greatest  difficulties.  A  chap- 
ter giving  a  fairly  full  description  of  the  methods  of 
elementary  analysis  follows,  and  then  a  chapter  on 
the  principles  of  physical  chemistry  as  applied  to 
molecular  weight  determinations  and  to  the  theories 
of  osmosis,  solution,  etc.  Those  facts  of  physical 
chemistry  which  it  is  desirable  to  call  attention 
to  that  are  not  included  in  this  chapter  are  inserted 
where  they  can  most  conveniently  be  studied  along 
with  the  organic  compounds.  The  remainder  of 
the  book  includes  a  description  of  the  various  groups 
of  organic  substances,  and,  where  possible,  there  is 
chosen,  as  the  representative  of  each  group,  some 
body  of  medical  or  biological  importance.  Numer- 
ous practical  exercises  accompany  the  text,  and  these 
have  been  chosen  and  arranged  so  as  to  occupy  about 
four  hours  of  laboratory  work  per  week  for  a  thirty- 


PREFACE  vii 

week  session.  A  few  more  advanced  exercises  are 
given  for  the  sake  of  completeness,  and  it  is  left 
to  the  teacher  whether  or  not  he  shall  have  them 
performed  by  the  student.  The  cyclic  compounds 
and  the  more  complicated  of  the  benzene  deriva- 
tives may  also  be  omitted  at  the  discretion  of  the 
teacher. 

In  the  Appendix  will  be  found  a  schedule  showing 
how  the  work  of  the  class  in  our  own  institution  is 
arranged  so  that  all  the  members  of  it  may  do  those 
experiments  involving  the  use  of  expensive  apparatus. 
The  laboratory  work  is  required  of  our  students.  We 
believe  that  by  conducting  an  elementary  analysis 
and  by  doing  cryoscopic  experiments  with  Beck- 
mann's  apparatus,  as  also  preparing  pure  organic 
compounds,  the  student  acquires  an  idea  of  accuracy 
and  an  insight  into  the  principles  of  chemical  methods 
which  he  cannot  otherwise  obtain,  and  which, 
without  any  doubt,  will  be  of  immense  value  to  him 
in  all  his  future  work.  Our  experience  is,  also, 
that  students  of  whom  laboratory  work  is  required 
get  a  grasp  and  understanding  of  the  subject  of 
organic  chemistry  such  as  others  rarely  acquire. 

H.  D.  HASKINS. 

J.  J.  R.  MACLEOD. 

April,  1907. 


CONTENTS 


CHAPTER  I. 

PAGE 

THE  NATURE  AND  COMPOSITION  OP  ORGANIC  COMPOUNDS  ...       1 


CHAPTER  II. 
PURIFICATION  AND  IDENTIFICATION  OF  SUBSTANCES 7 

CHAPTER  III. 
ELEMENTARY  ANALYSIS 28 

CHAPTER  IV. 

MOLECULAR  WEIGHT  DETERMINATION.  THE  NATURE  OF  SOLU- 
TIONS. OSMOTIC  PRESSURE.  IONIZATION.  SURF  ACE  TEN- 
SION. VISCOSITY.  COLLOIDAL  SOLUTIONS 40 

• 

CHAPTER  V. 

FORMULAE,  EMPIRICAL  AND  STRUCTURAL.    ISOMERISM 98 

SYNOPSIS  OF  CHAPTERS  I-V 100 

CHAPTER  VI. 

PRELIMINARY  SURVEY  OF  ORGANIC  CHEMISTRY 101 

SYNOPSIS  OF  FATTY  COMPOUNDS 115 

CHAPTER  VII. 

SATURATED  HYDROCARBONS.     METHANE  SERIES 117 

ix 


X  CONTENTS 

CHAPTER  VIII. 

PAGE 

HALOGEN  SUBSTITUTION  PRODUCTS  OF  THE  PARAFFINS 124 

CHAPTER  IX. 
ETHERS 132 

CHAPTER  X. 
PRIMARY  ALCOHOLS : . , 136 

CHAPTER  XI. 
ALDEHYDES 146 

CHAPTER  XII. 

FATTY  ACIDS  AND  ETHEREAL  SALTS.     FURTHER  OBSERVATIONS 

IN  PHYSICAL  CHEMISTRY 157 

CHAPTER  XIII. 

SECONDARY     AND     CERTAIN     OTHER     MONACID     ALCOHOLS. 

KETONES 189 

CHAPTER  XIV. 
DIACID  ALCOHOLS  AND  DIBASIC  ACIDS 193 

CHAPTER  XV. 

\ 
TRIACID  ALCOHOLS,  FATS,  AND  SOAPS 199 

CHAPTER  XVI. 
HYDROXY-ACIDS 212 

CHAPTER  XVII. 
CARBOHYDRATES  AND  GLUCOSIDES 227 

CHAPTER  XVIII. 

NITROGEN  DERIVATIVES.     (ALSO  PHOSPHORUS  AND  ARSENIC 
COMPOUNDS.) 255 


CONTENTS  xi 

CHAPTER  XIX. 

PAGE 

AMINO  ACIDS  AND  ACID  AMIDES 266 

CHAPTER  XX. 

ACID    IMIDES.     COMPLEX    AMINO    AND    IMIDO    COMPOUNDS, 

INCLUDING  POLYPEPTIDES 284 

CHAPTER  XXI. 

UNSATURATED  HYDROCARBONS  AND  THEIR  DERIVATIVES 299 

CHAPTER  XXII. 

SULPHUR  DERIVATIVES 306 

CHAPTER  XXIII. 
CYCLIC  AND  BI-CYCLIC  COMPOUNDS 309 

CHAPTER  XXIV. 
THE  AROMATIC  HYDROCARBONS 316 

CHAPTER  XXV. 

AROMATIC  HALOGEN  DERIVATIVES 333 

CHAPTER  XXVI. 
AROMATIC  HYDROXY  COMPOUNDS 336 

CHAPTER  XXVII. 
AROMATIC  ACIDS 356 

CHAPTER  XXVIII. 
AROMATIC  NITROGEN  DERIVATIVES.  .  .  374 


xii  CONTENTS 

CHAPTER  XXIX. 

PAGE 

SULPHUR  AND  ARSENIC  DERIVATIVES 391 

CHAPTER  XXX. 
QUINONES,  DYES  AND  INDICATORS 398 

CHAPTER  XXXI. 
AROMATIC  COMPOUNDS  HAVING  CONDENSED  RINGS 409 

CHAPTER  XXXII. 

HETEROCYCLIC  COMPOUNDS 414 

SYNOPSIS  OF  AROMATIC  COMPOUNDS 423 

CHAPTER  XXXIII. 
ALKALOIDS  AND  DRUG  PRINCIPLES 425 

APPENDIX. 

NOTE  TO  THE  INSTRUCTOR 443 

REFERENCE  TABLES 

I.  Specific  Gravity  and  Percentage  of  Alcohol 445 

II.  Weight  of   Pure  Gas  in  1  c.c.  of    Moist  Nitrogen  at 

Various  Temperatures  and  under  Various  Pressures . .  447 

III.  Specific  Gravity  and  Percentage  of  NaOH  in  Aqueous 

Solution 448 

IV.  Specific  Gravity  and  Percentage  of  KOH  in  Aqueous 

Solution 449 

V.  Acetic    Acid,    Specific    Gravity   and    Freezing-point   at 

Various  Concentrations 450 

VI.  Vapor  Tension  of  Water  and  of  40%  KOH  at  Various 

Temperatures 450 

VII.  Dissociation  Constants  of  Certain  Organic  Acids 451 

VIII.  Dissociation  Constants  of  Certain  Bases 451 

IX.  Power  of  Certain  Acids  to  Cause  Hydrolysis 452 


CONTENTS  xiii 

ILLUSTRATIONS. 

PAGE 

FIG.    1.  Melting-point  Apparatus 10 

2.  Sublimation  Apparatus — after  Gattermann 14 

3.  Fractional  Distillation  Apparatus — after  Gattermann.  15 

4.  Fractionating  Column— after  Gattermann 15 

5.  Steam  Distillation  Apparatus — after  Gattermann ....  16 

6.  Vacuum  Distillation  Apparatus — after  Gattermann. . .  17 

7.  Boiling-point  Flask 18 

8.  Picnometer 23 

9.  Westphal's  balance 23 

10.  Hydrometer 24 

11.  Combustion  furnace 30 

12.  Calcium  Chloride  and  Potash  Absorption  Apparatus — 
after  Gattermann 31 

13.  Mixing  Tube 32 

14.  Nitrogen  Burette — after  Gattermann 37 

15.  Victor    Meyer's    Vapor    Density    Apparatus — after 
Walker 45 

16.  Pfeffer's  Osmotic  Pressure  Apparatus 49 

17.  Beckmann's     Apparatus     and     Thermometer — after 
Walker 61 

18.  Flashing-point  Apparatus — after  Remsen 122 

19.  Ethyl  Bromide  Apparatus — after  Gattermann 126 

20.  Aldehyde  Apparatus — after  Fischer 152 

21.  Acetyl  Chloride  Apparatus — after  Gattermann 167 

22.  Tartaric  Acid  Models,  Illustrating  Stereoisomerism . .  .   223 

23.  Sodium  Ammonium  Racemate  Crystals — after  Holle- 
man 224 

24.  Ethylene  Bromide  Apparatus — after  Gattermann 301 

25.  Collie's  Benzene  Model .324 


ORGANIC  CHEMISTRY 


CHAPTER  I 

THE  NATURE  AND  COMPOSITION  OF  ORGANIC 
COMPOUNDS 

Definition  of  Organic  Chemistry.  The  various  inor- 
ganic chemical  compounds  are  classified  by  the  chem- 
ist into  groups,  a  group  comprising  all  the  com- 
pounds of  some  particular  element.  Thus  we 
have  the  iron  group,  the  sulphur  group,  and  so  on. 
On  account,  however,  of  the  great  number 1  of 
compounds  containing  the  element  carbon,  the  group 
of  carbon  compounds  is  set  apart  for  consideration 
as  a  special  branch  of  chemistry.  Organic  chem- 
istry is  that  branch:  it  is  the  chemistry  of  carbon 
compounds.  This  definition  is,  however,  not  strictly 
accurate,  for  it  is  customary  to  treat  of  the  oxides 
of  carbon  and  the  carbonates  in  inorganic  chemistry. 

The  name  organic  owes  its 'origin  to  the  old-time 
belief  that  these  compounds  of  carbon  could  be  pro- 
duced only  by  the  agency  of  vegetable  or  animal 
organisms,  by  so-called  vital  activity.  That  such  a 
notion  is  untenable  was  first  shown  by  Wohler, 
who,  in  1828,  obtained  urea — the  main  organic 
1  About  150,000. 


CHEMISTRY 


constituent  of  urine — by  simply  evaporating  an 
aqueous  solution  of  ammonium  iso-cyanate,  his 
intent  being  to  recrystallize  the  latter  salt  (p.  278). 
Since  that  date  thousands  of  organic  compounds 
have  been  prepared  in  the  laboratory  without 
any  assistance  from  vital  processes.  In  fact,  a  great 
proportion  of  the  compounds  known  to  organic 
chemists  have  never  been  discovered  in  nature, 
but  have  been  created  in  the  chemical  laboratory. 

Elements  and  Their  Detection.  In  organic  com- 
pounds carbon  may  exist  in  combination  with  one, 
two,  three,  four,  or  even  five  other  elements.  The 
most  important  elements  present  in  organic  com- 
pounds, together  with  their  atomic  weights  and 
valences,  are  as  follows: 

Carbon          C,  atomic  wt.  12,  valence  IV. 
Hydrogen,     H,      "        "    i,       "       I. 
Oxygen,         O,      "        "16,       "       II. 
Nitrogen,      N,      "        "14,       "       III  and  V. 
Phosphorus,?,      "        "31,       "       III  and  V. 
Sulphur,         S,      "        "32,      "       II,  IV  and  VI. 

Some  important  compounds  contain  the  halogens 
(Cl,  Br,  I).  The  presence  of  most  of  these  elements 
in  organic  compounds  can  be  quite  readily  detected 
by  simple  tests,  the  principal  ones  being  incorporated 
in  the  experiments  that  follow.  The  presence  of 
oxygen  cannot  be  directly  determined;  it  is  detected 
by  rinding  the  percentage  composition  of  the  com- 
pound and  observing  that  the  sum  of  the  per  cents 
of  all  the  other  elements  is  less  than  one  hundred. 


ORGANIC  COMPOUNDS  3 

EXPERIMENTS.  Detection  of  carbon,  hydrogen, 
nitrogen,  sulphur,  phosphorus  and  chlorine. 

(1)  C  and  H.     Dry  a  clean  test-tube  in  the  gas- 
flame.     Fit  it  with  a  cork  through  which  passes 
a  glass  tube  bent  at  a  right  angle.     Mix  in  a  mortar 
a  little  dry  cane  sugar  and  ten  times  as  much  dry 
CuO,  pour  this  mixture  into  the  test-tube,  cork,  and 
dip  the  outside  end  of  the  glass  tube  into  baryta 
solution  contained  in  another  test-tube.     Heat  the 
sugar  mixture  over  a  flame.     Drops  of  water  con- 
dense on  the  cool  parts,  showing  the  presence  of  H.1 
Cloudiness  in  the  baryta  is  due  to  carbon  dioxide, 
BaCOs    having    been    formed,    and    indicates    the 
presence  of  C.     By  heating,  CuO  is  reduced;    its 
oxygen  combines  with  the  C  and  the  H  of  the  organic 
substance  to  produce  CO2  and  EbO. 

(2)  N  and  S.     (a)  Triturate  in  a  mortar  some  dry 
albumin  with  twenty  times   as  much   soda-lime,2 
transfer  the  mixture  to  a  test-tube,  and  heat  over 
a  flame.     Test  the  vapor  that  appears  for  ammonia, 
the  presence  of  which  proves  the  existence  of  N  in 
the  compound  examined. 

(6)  Put  into  a  dried  test-tube  some  dry  albumin 
equal  in  bulk  to  a  bean.  Add  a  small  piece  of  clean 
metallic  sodium.  Heat  until  the  mass  is  red-hot, 
then  gently  drop  the  test-tube  into  a  mortar  contain- 
ing 10  c.c.  of  distilled  water.  The  tube  breaks, 
and  NaCN  and  Na2S  go  into  solution.  Grind 

1  Water  of  crystallization  must  be  removed  before  testing 
for  hydrogen. 

2  Soda-lime  is  made  by  gradually  adding  powdered  quick- 
lime to  a  saturated  solution  of  caustic  soda  with  constant  stirring. 


4  ORGANIC  CHEMISTRY 

up  the  charred  mass  with  the  pestle.  Filter  and 
divide  the  filtrate  into  portions  A,  B,  C,  and  D. 
To  A  add  NaOH  until  strongly  alkaline,  then  a  few 
drops  of  freshly  made  FeSO*  solution  l  and  a  drop 
of  FeCls  solution.  Boil  this  mixture  two  minutes, 
cool,  and  acidify  with  HC1.  The  appearance  of  a 
greenish-blue  color  or  a  precipitate  of  Prussian 
blue  indicates  N.  To  B  add  a  few  drops  of  a  fresh 
solution  of  sodium  nitroprusside;2  a  reddish-violet 
color  points  to  the  presence  of  S.  To  C  add  lead 
acetate  solution  and  acidify  with  acetic  acid.  A 
brownish-black  discoloration  or  precipitate  is  due 
to  S.  Neutralize  D  with  HC1;  add  a  few  drops  of 
FeCls  solution;  a  red  color,  which  is  removed  by 
HgCb,  is  caused  by  the  presence  of  sulphocyanide. 

If  sulphocyanide  is  not  formed  in  examining  an  organic 
compound  by  this  method  (it  is  not  formed  if  a  sufficient  excess 
of  sodium  is  used),  halogens  may  be  tested  for  in  the  filtrate 
by  boiling  some  of  it  with  one-tenth  volume  of  concentrated 
HN03  (HCN  or  H2S  driven  off,  prolonged  boiling  may  be 
necessary  to  remove  all  the  HCN)  and  then  testing  with 
AgN03  (precipitate  of  AgCl,  AgBr,  or  Agl).  In  this  test 
iodine  and  bromine  are  set  free  by  the  nitric  acid  and  can  be 
detected  by  conducting  the  vapor  into  a  test-tube  containing  a 
little  CS2  (for  this  test  heat  the  mixture  in  a  short  test-tube 
and  close  the  tube  with  a  stopper  having  a  bent  tube  as  in 
exp.  1). 

If  it  is  desired  to  detect  N,  S,  or  halogens  in  a  liquid  it  is 
best  to  drop  the  liquid  on  melted  sodium  contained  in  a  test- 
tube  that  is  held  vertically  by  being  thrust  through  a  hole  in 
an  asbestos  pad. 

1  Sodium  ferrocya'nide  is  formed  by  this  treatment. 
«  Formula  =Na2Fe(CN)6(NO). 


ORGANIC  COMPOUNDS  5 

(3)  Cl.  Put  a    little    pure    powdered    soda-lime 
in  a  dry  test-tube,  add  as  much  chloroform  as  it 
will  soak  up,  and  heat  strongly.     Break  the  tube 
and  powder  the  mass  in  a   mortar.     Treat  with 
strong  HNOs  until  dissolved.     Test  with  AgNOs. 
A  control  test  with  soda-lime  alone  should  give 
only  a  slight  turbidity. 

(4)  P.    Mix  some  dry  nucleoprotein  (or  dry  yeast) 
with  twenty  parts  of  fusion  mixture  (1  part  Na2COs 
+2  parts  KNOs).     Heat  in  a  crucible  until  the  mass 
is  almost  white.    When  cool,  dissolve  it  in  a  little 
hot  water  and  pour  the  resulting  solution  into  an 
evaporating  dish.     Add  HC1  until  neutral  and  filter. 
To  half  of  the  filtrate  add  NH4OH  until  strongly 
alkaline,  then  add  magnesia  mixture.1    The  phos- 
phates, formed  by  the  oxidation  of  the  phosphorus 
of  the  compound,  cause  a  white  precipitate.     To 
the  other  half  of  the  filtrate  add  HNOs  until  strongly 
acid,   then   add   an   equal  volume   of   ammonium 
molybdate  solution  2  and  heat  in  a  water  bath  until 
a  fine  yellow  precipitate  appears. 

Having  thus  determined  what  elements  are  pres- 
ent in  the  organic  compound  that  he  is  investigating, 
the  chemist  next  proceeds  to  its  more  thorough 

1  Magnesia  mixture  is  made  as  follows:    Dissolve  55  gm. 
of  pure  MgCl2  crystals  and  70  gm.  NH4C1  in  1300  c.c.  of  water 
and  add  350  c.c.  of  8%  ammonium  hydroxide. 

2  Ammonium  molybdate  solution  is  made  as  follows:    Dis- 
solve 75  gm.  of  powdered  ammonium  molybdate  in  250  c.c.  of 
water  with  the  aid  of  heat,  and  add  (when  cool)  35  c.c.  of 
C.P.  NH4OH.    Pour  this  into  a  mixture  of  300  c.c.  of  C.P. 
HN03  and  675  c.c.  of  water  while  stirring  vigorously. 


6  ORGANIC  CHEMISTRY 

examination.  He  first  estimates  the  percentage 
amounts  of  the  various  elements  contained  in  the 
substance,  and  then  he  determines  its  molecular 
weight.  He  is  able  from  these  data  to  calculate 
the  empirical l  formula.  But  more  than  one  sub- 
stance may  have  this  same  formula;  therefore  he 
studies  the  reactions  of  the  compound  when  treated 
with  reagents  in  order  to  get  a  clue  as  to  how  its 
molecule  is  built  up,  that  is,  how  its  atoms  are 
linked  together.  And,  finally,  by  causing  simpler 
substances,  the  structure  of  the  molecules  of  which 
is  known,  to  become  united  (synthesis),  he  endeavors 
to  produce  a  substance  having  the  same  molecular 
structure  as  his  compound.  If  his  synthetic  com- 
pound shows  properties  that  are  identical  with  the 
substance  under  examination,  the  chemist  then 
considers  that  he  has  established  with  absolute 
certainty  the  chemical  construction  of  the  com- 
pound. 

But  all  this  work  will  end  in  failure  unless  the  sub- 
stance under  examination  be  absolutely  pure,  i.e., 
free  from  admixture  of  any  other  substances.  It 
is  necessary  for  us  at  this  stage,  therefore,  to  explain 
the  chief  methods  of  purification  as  well  as  the 
tests  by  which  the  purity  of  the  substance  is  ascer- 
tained. This  will  be  done  in  the  chapter  that  follows. 

1  The  empirical  formula  gives  merely  the  total  number  of 
atoms  of  each  element  in  one  molecule,  as  C*Hi20«  (see 
p.  98). 


CHAPTER  II 

PURIFICATION  AND  IDENTIFICATION  OF 
SUBSTANCES 

PURIFICATION  OF  SUBSTANCES 

THE  main  methods  of  separating  an  organic  sub- 
stance in  a  pure  state  are  crystallization,  sublimation, 
distillation,  extraction  and  dialysis. 

Crystallization.  The  basis  of  this  method  is  the 
fact  that  different  substances  are  not  usually  solu- 
ble to  an  equal  extent  in  the  same  solvent.  For 
example,  acetanilide  can  be  separated  from  dex- 
trose by  dissolving  the  mixture  of  these  two  in  hot 
water;  when  the  resulting  solution  is  cooled,  the 
acetanilide  crystallizes  out  because  of  its  slight 
solubility  in  cold  water,  while  the  dextrose  remains 
in  solution.  By  repeated  crystallization  in  this 
manner  perfectly  pure  acetanilide  can  be  obtained 
(see  exp.  below). 

Inasmuch  as  crystallization  as  a  method  for 
separation  and  purification  of  organic  compounds 
is  invaluable,  it  will  be  well  to  detail  specific  direc- 
tions for  carrying  it  out.  (1)  Carefully  select  a 
suitable  solvent.  Put  small  quantities  of  the  sub- 
stance to  be  purified  into  several  test-tubes;  and 
add  to  each  a  different  solvent  (those  most  commonly 
used  are  water,  alcohol,  ether,  chloroform,  benzol, 

7 


8  ORGANIC  CHEMISTRY 

petroleum  ether,  acetone,  and  glacial  acetic  acid). 
Discard  those  that  dissolve  the  substance  readily. 
Heat  each  of  the  remaining.  Choose  the  solvent 
which  when  hot  dissolves  the  substance  readily,  but 
deposits  crystals  on  cooling.  The  solvent  should 
either  hold  the  impurity  in  solution  when  cold  or 
exert  no  solvent  action  on  it  whatever. 

(2)  Completely  saturate  at  boiling  temperature 
a  certain  quantity  of  the  chosen  solvent  with  the  sub- 
stance. 

(3)  Filter  the  hot  liquid  through  a  plaited  filter, 
using  a  funnel  with  a  short  stem.     (With  a  long- 
stemmed  funnel  crystals  may  separate  out  in  the 
stem  and  block  it.)     Heating  the  funnel  in  hot 
water  before  filtration  may  be  resorted  to. 

(4)  Collect   the   filtrate   in   a   beaker   having   a 
capacity  twice  the  volume   of  the   liquid.     With 
too  small  a  beaker  creeping  of  crystals  and  liquid 
may  occur. 

(5)  Cool  slowly.1     If  crystals  are  deposited  very 
quickly,  redissolve  with  the  aid  of  heat,  and  pre- 
vent rapid  cooling  by  wrapping  the  beaker  with  a 
towel. 

(6)  Cover  the  beaker  with  a  piece  of  filter-paper 
to  prevent   condensation-drops  from  falling  back 
into  the  liquid  and  disturbing  the  crystallization. 
A  watch-glass  or  glass  plate  completes  the  covering. 

(7)  Do  not  disturb  the  beaker  until  crystals  have 
formed.     If  their  appearance  is  greatly  delayed  they 
may  often  be  induced  to  form  by  scratching  the  inner 

1  5,  6,  and  7  may  be  disregarded  except  when  the  form  of  the 
crystals  is  to  be  studied. 


PURIFICATION  OF  SUBSTANCES  9 

wall  of  the  beaker  with  a  glass  rod,  or  by  "  sowing  " 
a  crystal  of  the  substance  into  the  liquid. 

(8)  If  the  substance  is  not  sufficiently  insoluble 
in  the  cold  solvent,  crystallization  may  be  brought 
about  by  slow  evaporation  in  a  loosely  covered 
crystallization  dish. 

(9)  Collect  the  crystals  on  a  suction-filter  (reject 
the  crystals  that  have  crept  above  the  surface  of  the 
liquid),  and  wash  them  with  a  little  of  the  pure 
cold  solvent. 

(10)  Dry  the  crystals  in  a  desiccator,  except  when 
they  contain  water  of  crystallization. 

EXPERIMENT.  Put  20  c.c.  of  distilled  water  into 
a  beaker  and  heat  to  boiling  on  an  asbestos  pad. 
Completely  saturate  it  with  the  mixture  of  dextrose 
and  acetanilide  which  is  furnished.  Filter  while 
hot,  and  cool  rapidly.  When  a  good  crop  of  crystals 
has  formed,  separate  them  by  filtration.  Dissolve 
in  a  little  water  and  recrystallize.  Repeat  the  proc- 
ess until  the  filtrate  from  the  crystals  no  longer 
gives  reduction  when  boiled  with  Fehling's  solution.1 
At  least  three  crystallizations  should  be  carried 
through.  Save  the  pure  white  crystals.  After 
they  are  dried  in  a  desiccator  a  determination  of 
the  melting-point  may  be  made  (see  below).. 

1  Fehling's  reagent  consists  of  an  alkaline  solution  of  cupric 
hydroxide,  the  latter  being  held  in  solution  by  means  of  Rochelle 
salt.  The  reagent  should  be  freshly  prepared  by  mixing  equal 
volumes  of  7%  CuS04  and  of  an  alkali  solution  containing 
25  gm.  KOH  and  35  gm.  Rochelle  salt  in  100  c.c.  The  reagent 
is  of  a  deep-blue  color,  and  when  it  is  boiled  with  even  a  trace 
of  dextrose  a  red  precipitate  forms  in  it. 


10  ORGANIC  CHEMISTRY 

To  test  the  purity  of  the  crystals  their  melting- 
point  is  determined.  The  method  of  making  a 
melting-point  determination  will  be  described  in 
the  experiments  that  follow.  Pure  crystals  melt 
quite  sharply  and  completely,  i.e.,  they  become 
completely  melted  within  0.5°  to  1°.  The  crystals 
may  be  considered  pure  when,  after  repeated  crystal- 
lization (preferably  from  different  solvents),  the 
melting-point  remains  constant  for  several  successive 
determinations.  A  bath  of  water  may  be  used  for 
substances  having  a  low  melting-point  (below  80°  l). 
Sulphuric  acid  is  used  for  higher  tem- 
peratures (up  to  280°).  For  still  higher 
temperatures  paraffin  is  used.  The 
thermometer  should  be  one  with  the 
scale  engraved  on  the  stem.  The  crys- 
tals should  be  powdered  and  thoroughly 
dried  in  a  desiccator. 


EXPERIMENT.       Make    melting-point 
tubes  by  heating  a  glass  tube  of  10  mm. 
diameter  in  a  flame  until 
a   2-cm.    section    is   red, 
then  drawing  it  out.    A 
capillary    tube    about    1 
mm.  in  diameter  and  5 
FlG-  *•  or   6   feet   long,   is   thus 

obtained.  Break  into  lengths  of  6-8  cm.  and  seal 
one  end  of  each.  Put  into  such  a  tube  some 
powdered  chloral  hydrate  that  has  been  dried 
in  a  desiccator.  Gentle  scratching  with  a  file 
1  All  temperatures  given  in  this  book  are  centigrade. 


PURIFICATION  OF  SUBSTANCES  11 

will  cause  the  particles  to  travel  to  the  bottom 
of  the  tube.  Attach  the  tube  to  a  thermometer 
by  means  of  a  narrow  rubber  band  cut  off  from 
rubber  tubing,  adjusting  it  so  that  the  main  part 
of  the  chloral  will  be  opposite  the  middle  of  the 
bulb  of  the  thermometer.  Suspend  the  ther- 
mometer in  a  beaker  of  water  so  that  the  bulb  is 
fully  immersed.  Heat  the  water  very  gradually. 
Note  the  temperature  at  which  there  is  the  first 
indication  of  melting  (beginning  transparency  or 
collapsing  against  the  wall  of  the  capillary  tube  of 
any  portion  of  the  crystalline  substance).  Note 
also  the  temperature  of  complete  fusion.  The 
temperature  nearest  to  the  true  melting-point  is 
that  recorded  by  the  thermometer  at  the  moment 
when  minute  droplets  are  first  formed  by  the  melt- 
ing of  the  fine  particles  that  are  in  actual  contact 
with  the  wall  of  the  capillary  tube. 

Into  another  tube  put  pure  dried  powdered  urea;1 
attach  the  tube  to  a  thermometer  with  a  fine  plati- 
num wire,  adjusting  it  as  above.  The  bath  in 
this  case  should  be  pure  H2S04  containing  30% 
of  K2SO4  (to  lessen  fuming),  contained  in  a  long- 
necked  Jena  flask  (as,  for  example,  a  Kjeldahl 
incineration-flask).  By  means  of  a  loosely  fitting 
cork  suspend  the  thermometer  in  the  flask,  with 
its  bulb  dipping  into  the  bath.  In  a  similar  manner 
suspend  another  thermometer  to  take  the  temper- 
ature of  the  air  above  the  H2S04.  Heat  gradually. 
When  melting  occurs,  place  the  bulb  of  the  second 

1  Where  "  pure  urea  "  is  called  for  it  is  best  to  prepare  it 
by  recrystallizing  some  urea  from  hot  absolute  alcohol. 


12  ORGANIC  CHEMISTRY 

thermometer  midway  between  the  meniscus  of  the 
mercury  in  the  stem  of  the  first  thermometer  and 
the  surface  of  the  bath;  from  this  quickly  make 
the  reading  of  the  air  temperature  (this  is  t  in  the 
formula  below).  Also  measure  in  degrees  the 
height  of  the  mercury  column  above  the  surface 
of  the  H2S04  ( =L  in  the  formula).  The  correction 
that  must  be  added  to  the  observed  reading  (which 
is  T)  on  account  of  the  fact  that  the  stem  of  the 
thermometer  and  mercury  thread  is  cooler  than  the 
bulb,  can  be  calculated  by  the  formula:  L(T  —  t) 
(0.000154).  The  coefficient  of  expansion  of  mer- 
cury in  glass  is  0.000154.  The  corrected  1  melting- 
point  of  pure  urea  is  132.6°. 

For  the  most  accurate  work  in  determining  melting-points 
careful  attention  to  a  number  of  things  is  essential.  Tested 
thermometers  of  a  standard  thickness  should  be  used.  A  set 
of  thermometers  of  limited  range,  as  0-50°,  50-100°,  100-150° 
graduated  for  0.2°,  would  be  desirable.  The  melting-point 
tube  should  have  about  the  same  thickness  of  wall  as  the  wall 
of  the  bulb  of  the  thermometer. 

The  crushed  crystals  should  be  sifted  through  a  fine-mesh 
screen,  as  variation  in  size  of  the  particles  gives  variation  in 
melting-point.  The  tube  should  be  filled  for  only  about  3 
mm.  of  its  length,  solidly  packed.  The  initial  heating  may  be 
rapid  until  a  temperature  20°  below  the  melting-point  is  reached, 
when  the  heating  should  be  such  as  to  cause  not  over  3°  rise 
per  minute,  and  near  the  melting-point  0.5°  per  minute.  Stir- 
ring of  the  bath  is  desirable.  A  double  bath  by  means  of 
which  the  air  about  the  thermometer  is  heated  as  well  as  the 
liquid  insures  greater  accuracy.  Such  an  apparatus  can  be  con- 

1  The  melting-points  marked  "  corrected  "  are  quoted  from 
H.  Meyer's  Analyse  und  Konstitution  der  organischen  Verbind- 
ungen. 


PURIFICATION  OF  SUBSTANCES  13 

structed  by  taking  a  tall  Jena  beaker  (17-20  by  8  cm.)  and 
suspending  in  it  a  large  test-tube  (20x3  cm.).  Pour  into  the 
test-tube  albolene  (liquid  vaseline)  to  a  depth  of  5  cm.,  and  fill 
the  beaker  for  nine-tenths  of  its  depth  with  the  same  liquid. 
As  a  stirrer  use  a  piece  of  gold-plated  wire,  coiled  in  a  large 
spiral  at  the  end  to  fit  loosely  the  inside  of  the  test-tube.  Sus- 
pend the  thermometers  in  the  test-tube  as  shown  in  Fig.  1. 
When  the  temperature  approaches  the  melting-point,  stir 
steadily.  An  air  temperature  of  only  3-7°  below  the  oil  tem- 
perature is  secured,  hence  it  is  unnecessary  to  calculate  a  cor- 
rection. 

A  method  of  purification  applicable  to  certain 
solid  substances  is  sublimation.  A  substance  sub- 
limes when  it  passes  readily  from  the  solid  state  to 
a  vapor.  The  method  is  carried  out  as  follows :  A 
watch-glass  or  evaporating  dish  containing  the 
substance  is  covered  with  iilter-paper  which  has 
several  pin-hole  perforations.  A  funnel  of  slightly 
smaller  diameter  is  inverted  over  this,  the  stem 
being  loosely  plugged  with  cotton.  The  dish  is 
heated  gradually  until  vapor  passes  into  the  upper 
chamber  of  the  apparatus  and  condenses  on  the 
cool  walls  of  the  funnel  (see  exp.,  p.  359). 

Distillation.  This  method  is  useful  mainly  for 
the  purification  of  liquids.  Certain  solid  substances, 
however,  can  be  distilled  to  advantage.  When 
the  impurity  is  a  material  that  will  not  vaporize 
at  the  temperature  employed  (i.e.,  at  a  temperature 
at  which  the  substance  itself  readily  vaporizes), 
simple  distillation  suffices.  When,  however,  a  mix- 
ture of  volatilizable  liquids  is  dealt  with,  fractional 
distillation  has  to  be  resorted  to.  This  method  is 
described  in  the  following  experiment.  Certain 


14  ORGANIC  CHEMISTRY 

mixtures  cannot  be  resolved  into  their  constituents 
in  the  pure  state  by  fractional  distillation,  such  as 
water  and  alcohol,  or  methyl  alcohol  and  benzol. 

EXPERIMENT.  Set  up  a  distillation  apparatus  as 
shown  in  the  diagram.  Into  the  distilling  flask 
pour  through  a  funnel  about  300 
c.c.  of  70%  alcohol,  and  drop  in 
some  short  capillary  tubes.  Select 
a  cork  that  will  fit  the  flask 
tightly.  Through  a  hole  in  the 
cork  insert  a  thermometer,  and 
hang  it  so  that  the  bulb  is  in  the 
stream  of  vapor,  i.e.,  opposite  or 
below  the  opening  of  the  side  tube. 
The  bulb  must  not  be  below  the 
neck  nor  low  enough  to  be  splashed 
by  the  boiling  liquid.  Heat  on  a  water  bath.  Have 
four  clean  dry  receiving  flasks  ready  and  labeled.  In 
the  first  flask  collect  all  the  distillate  coming  over 
while  the  thermometer  registers  a  temperature 
between  78°  and  83°.  Now  dry  the  outside  of  the 
distilling  flask  with  a  cloth  and  change  it  to  an 
asbestos  pad  having  a  hole  one  inch  in  diameter. 
In  the  second  flask  collect  that  distilling  between 
83°  and  88°.  Flask  number  three  is  to  catch  the 
distillate  between  88°  and  93°.  The  last  flask  re- 
ceives all  that  distills  over  above  93°.  (Do  not 
distill  over  all  the  water.)  Measure  the  amount  of 
each  fraction,  and  of  the  residue  in  the  flask.  Drain 
and  dry  the  condenser  tube. 

For  the  second  distillation  use  a  smaller  distilling 


PURIFICATION  OF  SUBSTANCES 


15 


flask  or  a  small  flask  with  a  bulbed  column  attached 
as  shown  in  the  diagram.     Pour  into  it  the  fluid  in 


FIG.  3. 

flask  number  one  and  use  the  latter  as  the  first 
receiving  flask  for  the  distillate.  When  the  tem- 
perature reaches  80°  pour  the  con- 
tents of  flask  number  two  into  the 
distilling  flask,  and  when  the  tem- 
perature again  rises  to  80°  replace 
flask  number  one  by  flask  number 
two  as  the  receiver;  also  change  the 
distilling  flask  to  the  asbestos  pad 
as  before.  When  the  temperature 
reaches  83°  add  the  liquid  in  flask 
number  three  to  the  distilling 
flask,  and  distill  until  the  tempera- 
ture reaches  88°. 

Determine  the  per  cent  of  alcohol  in  these  three 
fractions  by  taking  the  specific  gravity  of  each  with 
WestphaPs  balance  (see  p.  24),  and  comparing  with 
the  table  (p.  445).  By  repeated  fractionating 


FIG.  4. 


16 


ORGANIC  CHEMISTRY 


practically  all  of  the  alcohol  is  brought  into  flask 
number  one,  and  most  of  the  water  into  flask 
number  four.  As,  however,  it  is  simply  the  alcohol 
that  is  of  value  in  this  case,  redistill  the  first  frac- 
tion only  and  secure  a  distillate  coming  over  at 
78-79°.  This  should  contain  at  least  90%  (by 
volume)  of  alcohol. 

Distillation  is  sometimes  carried  out  by  bubbling 
steam  through  the  mixture,  which  is  kept  at  a  tem- 


FIQ.  5. 

perature  of  at  least  100°.  By  this  means  substances 
that  boil  even  at  200°  can  be  obtained  in  the  dis- 
tillate, mixed,  of  course,  with  a  large  quantity  of 
water  (see  Fig.  5).  Those  substances  that  do  not 
have  a  distinct  vapor  pressure  at  100°  will  not  dis- 
till with  steam. 

Vacuum  distillation  is  employed  in  certain  cases, 
particularly  when  it  is  desirable  to  lower  the  boil- 
ing-point in  order  to  prevent  any  decomposition 
of  the  substance.  Many  substances  decompose 
at  a  temperature  below  their  boiling-points.  The 


PURIFICATION  OF  SUBSTANCES  17 

distilling  apparatus  is  closed  up  air-tight  except 
for  a  finely  pointed  tube  which  dips  below  the  sur- 
face of  the  heated  liquid  and,  passing  through 
the  stopper,  is  open  to  the  air;  through  this  tube 
fine  bubbles  of  air  keep  the  contents  of  the  flask 
in  commotion  and  prevent  bumping.  The  receiv- 
ing flask  is  connected  with  a  suction-pump.  A 
reduction  of  pressure  in  the  apparatus  to  30  mm.  of 
mercury  (atmospheric  pressure  being  about  760  mm.) 


FIG.  6. 

will  usually  lower  the  boiling-point  of  a  high-boiling 
substance  by  nearly  100°.  An  ordinary  suction- 
pump  is  usually  quite  satisfactory  for  lowering  the 
pressure  (see  Fig.  6). 

The  test  of  purity  of  a  substance  that  distills  is  con- 
stancy of  boiling-point.  If,  after  repeated  frac- 
tional distillation,  a  material  is  obtained  which  has 
the  same  boiling-point  each  time  and  which  distills 
over  completely  at  that  temperature,  it  is  most 
likely  to  be  a  pure  substance. 


18  ORGANIC  CHEMISTRY 

EXPERIMENT.  The  boiling-point  flask  should  be 
either  a  long-necked  distilling  flask  which  has  the 
side  tube  coming  off  very  high  up  near  the  cork, 
or  an  ordinary  distilling  flask 
into  the  neck  of  which  is  fitted 
an  open  tube  slightly  ex- 
panded at  the  lower  end  so 
as  to  fit  the  neck,  while  the 
latter  has  been  dented  with  a 
blast-flame  at  the  proper  point 
to  prevent  the  tube  from  slip- 
ping into  the  chamber  of  the 
flask  (see  Fig.  7).  In  such  an 
apparatus  the  vapor  passes  up 

to  the  cork,  then  descends  outside  the  tube,  heating 
the  stem  of  the  thermometer  for  the  whole  length 
of  the  mercury  column,  the  thermometer  being 
lowered  sufficiently  to  permit  this. 

The  thermometer  used  should  be  of  the  same  kind 
as  those  specified  for  melting-point  determination 
(p.  12). 

Put  20  c.c.  of  pure  chloroform  into  the  flask; 
support  the  flask  on  wire  gauze  (it  is  advisable  to 
interpose  between  the  gauze  and  the  flask  an 
asbestos  pad  having  a  hole  one  inch  in  diameter). 
Attach  a  long  tube  as  an  air-condenser  and  place 
a  receiving  flask  in  position.  Heat  with  a  small 
flame.  When  vapor  passes  freely  into  the  con- 
denser, note  the  temperature.  Continue  distilla- 
tion until  the  temperature  has  remained  constant 
for  at  least  five  minutes.  Take  the  reading  as  the 
boiling-point.  No  correction  is  necessary  except 


PURIFICATION  OF  SUBSTANCES  19 

for  barometric  pressure.  This  correction  can  be 
calculated  approximately  by  adding  to  the  ob- 
served boiling-point  0.038°  for  each  mm.  below  760 
mm.  barometric  pressure  or  subtracting  0.038° 
for  each  mm.  above  this.1  The  boiling-point  of 
chloroform  at  760  mm.  pressure  is  61.2°  (corrected).2 

The  author  has  devised  a  simple  apparatus  by  which  the 
boiling-point  can  be  determined  under  standard  pressure 
without  the  calculation  of  a  correction.3 

The  special  distilling  flask  (see  Fig.  7)  is  connected  with  an 
air-tight  condensing  apparatus,  a  filtering  flask  (as  receiver) 
being  fitted  to  the  end  of  the  condenser.  The  side  tube  of 
this  flask  is  connected  with  tubing  containing  air  under  pressure 
coming  from  the  blower  part  of  a  large  Wetzel  suction  pump. 
A  calcium  chloride  tube  or  tower  is  interposed  to  prevent 
moisture  getting  into  the  flask.  The  compressed-air  system 
is  connected  also  with  a  barometer  (or  with  a  second  distilling 
apparatus,  as  suggested  below)  of  the  older  type  bent  in  U 
form  at  the  bottom;  and  furthermore  is  connected  with  a 
tube  that  is  suspended  in  a  tall  cylinder  of  water.  By  raising 
or  lowering  this  tube,  the  pressure  in  the  distilling  apparatus 
as  recorded  by  the  barometer  can  be  brought  to  any  height 

1  If  the  boiling-point  is  around  100°  the  factor  of  correction 
is  0.044,  if  150°  it  is  0.05,  if  200°  it  is  0.056,  and  if  250°  it  is  0.062. 
For  water,  alcohol,  organic  acids,  and  other  liquids  whose  mole- 
cules become  associated  (p.  69)  the  figures  are  lower;   around 
50°  it  is  0.032,  100°  it  is  0.037,  150°  it  is  0.042,  200°  it  is  0.046, 
and  250°  it  is  0.051. 

2  The  boiling-points  marked  "  corrected  "  in  this  book  are 
those  given  in  Traube's  Physico-chemical  Methods. 

3  Smith  and  Menzies   have  recognized  the   desirability  of 
securing  the  boiling-point  at  this  standard  pressure.    They 
recently  (1910)  described  an  apparatus  for  the  purpose.    Their 
method,  however,  makes  use  of  a  small  boiling-point  bulb 
tied  to  a  thermometer,  and  submerged  in  a  bath. 


20  ORGANIC  CHEMISTRY 

which  could  occur  as  atmospheric  pressure.  It  must  be  remem- 
bered that  a  small  correction  of  the  barometer  must  be  made 
for  the  temperature,  since  standard  barometric  pressure  is 
760  mm.  when  the  scale  and  the  mercury  of  the  barometer  are 
at  0°.  For  example,  if  the  temperature  of  the  room  is  15°,  the 
apparent  pressure  in  the  apparatus  must  be  762  mm.  (761.9  mm. 
if  the  barometer  has  a  brass  scale),  in  order  to  get  the  boiling- 
point  under  760  mm.  pressure. 

The  apparatus  can  be  used  to  demonstrate  the  amount  of 
change  of  boiling-point  for  definite  changes  of  pressure. 

After  accurately  determining  the  boiling-point  of  an  absolutely 
pure  liquid  that  is  stable  and  not  inclined  to  absorb  moisture 
(as  benzene),  the  apparatus  can  be  arranged  to  eliminate  the 
barometer  by  connecting  a  second  air-tight  distilling  apparatus 
in  which  to  boil  the  liquid  that  is  under  examination.  Now 
regulate  the  pressure  so  that  the  liquid  of  known  boiling-point 
distills  at  a  temperature  corresponding  to  standard  pressure 
as  previously  determined  (read  to  0.1°);  then  the  temperature 
at  which  the  other  liquid  distills  will  be  the  boiling-point  of 
the  latter  at  760  mm. 

If  the  liquid  has  a  high  boiling-point,  shield  the  flask  with  a 
metal  or  asbestos  cylinder  that  rests  on  the  asbestos  pad. 

Extraction.  Not  infrequently  the  most  feasible 
method  of  separating  an  organic  compound  from 
a  mixture  is  by  extraction.  It  may  be  extracted 
from  an  aqueous  mixture  by  shaking  the  latter 
with  an  organic  solvent  that  is  immiscible  with 
water.  If  the  substance  that  is  to  be  extracted  has 
a  greater  solubility  in  the  organic  solvent  than  in 
water,  it  will  be  extracted  rapidly.  In  many 
cases  the  solubility  of  the  substance  in  the  water 
may  be  greatly  diminished  by  saturating  the  solu- 
tion with  a  salt  (as  NaCl  or  CaCl2),  then,  of  course 
it  will  be  more  readily  extracted.  The  principle 
involved  in  extraction  is  that  a  substance  soluble 


PURIFICATION  OF  SUBSTANCES  21 

in  two  liquids  distributes  itself  between  the  two 
in  the  ratio  of  its  solubilities  in  the  two  solvents. 
For  instance,  if  a  compound  in  aqueous  solution 
is  twice  as  soluble  in  ether  as  in  water,  then  after 
shaking  the  solution  with  an  equal  volume  of  ether 
for  a  proper  length  of  time,  the  ether  will  contain 
two-thirds  of  the  substance  and  one-third  will  remain 
in  aqueous  solution.  It  follows  that  several  succes- 
sive extractions  with  small  portions  of  solvent  is 
very  much  more  efficient  than  a  single  extraction  with 
a  large  volume  of  the  solvent.  If  the  solubilities 
are  in  the  ratio  of  one  to  two  (as  above),  extracting 
once  by  shaking  thoroughly  with  three  volumes  of 
ether  will  result  in  one-seventh  of  the  original 
amount  remaining  in  aqueous  solution;  but  only 
one-twenty-seventh  will  remain  if  the  shaking  is 
carried  out  three  times  with  equal  volumes  of 
ether. 

If  the  solvent  is  one  that  takes  up  more  than  a 
trace  of  water,  a  drying  agent  should  be  used  to 
remove  the  water.  The  substance  extracted  is 
recovered  by  distillation  or  evaporation  of  the 
solvent.  If  necessary,  it  may  be  purified  further  by 
crystallization,  distillation,  or  by  treatment  with  a 
different  solvent. 

EXPERIMENT.  Measure  into  a  separating  fun- 
nel 20  c.c.  of  saturated  salicylic  acid  solution  and 
20  c.c.  of  ether,  stopper  tightly,  and  shake  vigor- 
ously for  ten  minutes.  Draw  off  the  bottom  layer, 
and  carefully  pour  the  ether  out  through  the  mouth 
of  the  funnel  into  a  dry  flask.  Return  the  aqueous 


22  ORGANIC  CHEMISTRY 

solution  to  the  funnel,  add  20  c.c.  of  ether,  and 
continue  as  above.  Also  extract  with  a  third  por- 
tion of  ether.  Test  about  1  c.c.  of  the  aqueous 
solution  with  a  drop  of  dilute  FeCls,  and  compare 
the  faint  color  reaction  with  the  intense  color  given 
by  saturated  salicylic  acid.  Treat  the  com- 
bined ether  extract  with  a  small  amount  of  dried 
Na2S(>4.  After  it  has  stood  for  some  time,  pour 
the  ether  into  a  dry  flask,  and  distill  off  most  of  the 
ether,  using  a  hot  water  bath  or  a  steam  bath  (have 
no  flames  near  by).  Now  transfer  the  balance  of 
the  ether  solution  to  an  evaporating  dish,  and  let 
the  ether  evaporate.  Note  that  an  appreciable 
quantity  of  crystalline  residue  is  obtained. 

Dialysis  is  occasionally  employed  for  purification 
purposes,  especially  in  biochemistry.  It  depends 
on  the  well-known  fact  that  crystalloids  can  diffuse 
through  animal  membranes  or  parchment  paper, 
whereas  colloids  cannot.  Thus,  to  separate  sodium 
chloride  from  egg  protein  a  solution  containing  these 
is  placed  in  a  dialyzer  suspended  in  pure  running 
water:  the  sodium  chloride  diffuses  out,  leaving 
the  egg  protein  in  the  dialyzer, 

IDENTIFICATION  OF  SUBSTANCES 

When  the  substance  has  been  purified  by  the  above 
methods,  identification  may  be  attempted.  For 
this  purpose  its  physical  properties  are  studied; 
its  color,  odor,  and  taste  are  carefully  noted,  and 
determinations  are  made  of  its  melting-point, 
boiling-point,  crystalline  form — including  measure- 


IDENTIFICATION  OF  SUBSTANCES  23 

ment  of  the  angles  of  the  crystals, — density  or  specific 
gravity,  action  on  polarized  light,  spectroscopic 
appearance,  refractive  power,  and  solubilities.  The 
data  thus  obtained  are  compared  with  those  of 
known  substances. 

Aside  from  the  first  five  properties  mentioned,  the 
most  universally  useful  one  for  purposes  of  identi- 
fication is  specific  gravity.  The  method  of  determin- 
ing this  will  be  considered  next.  Descriptions  of  the 


FIG.  8.  FIG.  9. 

methods  of  ascertaining  other  properties  will  be 
found  in  the  larger  laboratory  manuals.1 

The  specific  gravity  of  liquids  may  be  found  by 
several  different  methods:  1.  The  weight  of  equal 
volumes  of  the  liquid  and  of  water  may  be 
successively  determined  in  a  special  stoppered  bottle 
called  a  picnometer.  The  temperature  of  both 
fluids  at  the  moment  of  weighing  must  be  reported. 

1  Gatterman.  The  Practical  Methods  of  Organic  Chemis- 
try. Translated  by  Schober. 

Mulliken.    Identification  of  Pure  Organic  Compounds. 

Lassar-Cohn.  Laboratory  Manual  of  Organic  Chemistry; 
also,  Arbeitsmethoden  fur  organisch-chemische  Laboratorien. 


24  ORGANIC  CHEMISTRY 

The  temperature  of  the  water  taken  as  the  stand- 
ard for  comparison  may  be  0°,  4°,  or  15°.  The 
most  convenient  form  of  picnometer  is  one  which 
holds  exactly  10,  25,  or  50  gm.  of  pure  boiled  water 
at  15°  (see  Fig.  8).  Further  details  are  explained 
in  the  experiment  below. 

2.  Westphal's  balance  is  a  very  useful  instrument 
for  finding  specific  gravity  (see  Fig.  9).  Riders  of 
different  sizes  are  used  on  this  balance,  each  one 
representing  a  different  decimal  place  in  the  specific 
gravity.  This  instrument  gives  the  specific  gravity 
of  the  liquid  at  the  temperature  of  observa- 
tion compared  with  pure  water  at  15°. 

3.  The  hydrometer  is  another  empirically 
graduated  instrument  for  determining  specific 
gravity,  water  at  15°  being  the  standard.  It 
is  a  glass  float  having  a  long  stem;  this  sinks 
in  the  liquid,  so  that  the  surface  of  the  latter 
is  on  a  level  with  a  certain  mark  on  the 
stem,  and  the  figures  that  are  read  off  at 
that  mark  indicate  the  specific  gravity  (see 
Fig.  10). 

The  urinometer  is  a  hydrometer  for  use 
with  urine. 

The  specific  gravity  of  a  solid  can  be  found 
(ft)      by  weighing  it  in  the  air,  then  reweighing  it 
while  immersed  in  water.     This  method  has 
very  little  application  in  organic  chemistry. 
The  specific  gravity  of  crystals  or  small  solids  can 
be  determined    by  placing  an   accurately  weighed 
quantity  of  them  in  a  picnometer  filled  with  some 
liquid  in  which  they  are  insoluble  (see  exp.  below). 


IDENTIFICATION  OF  SUBSTANCES  25 

EXPERIMENTS,  (a)  Specific  gravity  of  petroleum 
ether.  Weigh  accurately  an  empty  dry  picnometer 
which  will  hold  just  25  gm.  of  pure  water  at  15°; 
deduct  from  the  weight  0.027  gm.  for  the  weight  of 
the  contained  air.  Remove  the  stopper  and  fill  with 
petroleum  ether  (boiling  at  60-70°).  Wrap  a  strip 
of  folded  filter-paper  about  the  neck  to  catch  the 
overflow,  insert  the  stopper  so  that  no  air  is  left  in 
the  bottle,  wipe  off  gently,  and  re  weigh.  When 
weighed,  note  the  temperature  as  indicated  by  the 
thermometer  in  the  stopper,  and  observe  whether 
air  has  been  drawn  into  the  bottle* by  cooling  and 
consequent  contraction  of  the  fluid.  The  difference 
between  the  two  weights  gives  the  weight  of  the 
petroleum  ether,  and  this  divided  by  the  weight  of 
an  equal  amount  of  water  (25  gm.)  gives  the  specific 
gravity  as  compared  with  water  at  15°.  In  record- 
ing specific  gravity  report  the  temperature  of  obser- 

18° 

vation;    for  example,  petroleum  ether  /Sr-^=0.67 

lo 

means  that  the  specific  gravity  of  petroleum  ether 
at  18°  is  0.67  when  compared  with  water  at  15°. 
Also  determine  the  specific  gravity  of  the  ether 
with  the  Westphal  balance. 

(6)  Specific  gravity  of  urea.  Weigh  a  little  test- 
tube  which  contains  pure  dry  urea  crystals.  Re- 
move the  stopper  of  the  picnometer  and  pour  the 
urea  into  the  petroleum  ether.  Tap  the  picnometer 
to  cause  the  air  adhering  to  the  crystals  to  be  dis- 
lodged. Now  fill  the  neck  with  more  petroleum 
ether,  insert  the  stopper  as  before,  and  reweigh. 
The  petroleum  ether  must  be  at  the  same  temper- 


26  ORGANIC  CHEMISTRY 

ature  as  before.  Reweigh  the  urea  tube;  by  deduct- 
ing this  weight  from  the  previous  one  find  the  weight 
of  the  urea  in  the  picnometer.  To  find  how  much 
petroleum  ether  has  been  displaced  by  the  urea 
'(the  latter  being  insoluble  in  the  former)  add  to 
the  weight  of  the  bottle  filled  with  petroleum 
ether  (exp.  a)  the  weight  of  the  urea,  then  deduct 
from  this  sum  the  weight  of  the  bottle  containing 
urea  immersed  in  petroleum  ether;  the  difference 
is  the  weight  of  the  petroleum  ether  displaced. 
Divide  this  by  the  specific  gravity  of  petroleum 
ether;  the  result  indicates  the  displacement  in 
cubic  centimeters,  or  rather  the  weight  (in  grams) 
of  an  equal  quantity  of  water,  so  that  the  weight 
of  the  urea  used  divided  by  this  figure  gives  the 
specific  gravity.  The  specific  gravity  of  urea  is 
about  1.33. 

If  the  substance  under  investigation  is  known  to 
chemists  it  can  generally  be  identified  by  comparing 
the  data  gathered  as  to  its  properties  with  tabulated 
lists  1  of  boiling-points,  melting-points,  specific 
gravities,  etc.  Generally  an  accurate  determina- 
tion of  the  boiling-  or  melting-point  and  of  the 
specific  gravity  will  definitely  locate  the  substance. 
When  dealing  with  a  liquid  it  is  advisable,  if  there 
exists  any  doubt  about  the  nature  of  the  substance, 
to  determine  the  specific  gravity  at  several  different 


tables  may  be  found  in  Physikalisch-chemische 
Tabellen  by  Landoldt  and  Bornstein,  Chemiker-Kalendar  by 
Biedermann  (yearly]editions),  Melting-  and  Boiling-Point  Tables 
by  Carnelly. 


IDENTIFICATION  OF  SUBSTANCES  27 

temperatures.  When  relying  on  melting-point  for 
identification,  it  is  of  value  to  bear  in  mind  that 
two  different  substances  may  have  nearly  the  same 
melting-point,  but  a  mixture  of  them  melts  at  a  far 
different  temperature.  Therefore,  mix  some  of  the 
known  substance  with  that  which  is  supposed  to  be 
identical  with  it  and  determine  melting-point; 
if  this  is  the  same  as  for  the  unknown  substance, 
then  identification  has  been  completed. 

If  the  substance  is  still  unknown  or  cannot  be 
positively  identified,  an  accurate  analysis  is  made  to 
determine  the  percentage  by  weight  of  each  element 
present  in  it. 


CHAPTER   III 
ELEMENTARY  ANALYSIS 

The  estimation  of  the  carbon  and  hydrogen  pres- 
ent in  a  compound  is  made  by  combustion  in  the 
presence  of  cupric  oxide,  the  end-products  of  com- 
bustion being  carbon  dioxide  and  water.  The 
method  is  in  principle  exactly  the  same  as  that 
for  the  detection  of  carbon  and  hydrogen. 

The  combustion  is  carried  out  in  a  glass  tube  of 
difficultly  fusible  glass  having  an  inside  diameter  of 
about  1.5  cm.  This  tube  should  be  10  cm.  longer 
than  the  furnace  in  which  it  is  to  be  heated;  85  cm. 
is  a  good  length.  A  tube  of  this  length  is  charged 
for  combustion  as  follows:  a  short  roll  or  spiral  of 
copper  gauze  is  inserted  and  pushed  in  5  cm.  from 
the  end;  moderately  coarse  cupric  oxide  (of  wire 
form)  is  poured  into  the  other  end  until  it  occupies 
35-40  cm.  of  the  tube  next  to  the  spiral;  then  another 
short  copper  spiral  is  pushed  down  to  the  coarse 
oxide  to  hold  the  latter  in  place.  The  next  20  cm. 
of  the  tube  is  occupied  by  the  substance  to  be 
analyzed  mixed  l  intimately  with  fine  cupric  oxide 

1  The  substance  may  be  placed  in  a  little  platinum  or  porce- 
lain boat  instead  of  being  mixed  with  CuO.  If  a  liquid  is  to 
be  analyzed  it  is  sealed  in  a  little  glass  bulb  having  a  long 
capillary  tube  and  the  tip  of  the  tube  is  broken  off  when  the 
bulb  is  placed  in  the  boat. 

28 


ELEMENTARY  ANALYSIS  29 

(wire  form)  in  the  manner  described  in  the  experi- 
ment below.  A  short  copper  spiral  (which  has  a 
wire  loop  attached)  is  inserted  and  finally  some 
coarse  cupric  oxide  may  be  added.  Each  end  of 
the  tube  is  closed  with  a  rubber  stopper.  Through 
the  stopper  at  the  end  nearest  the  fine  oxide  mixture 
passes  a  glass  tube,  which  is  connected  with  the 
apparatus  for  purifying  the  incoming  air  or  oxygen. 
The  absorption  apparatus  which  collects  the  prod- 
ucts of  combustion  is  connected  directly  with  a 
glass  tube  passing  through  the  stopper  at  the  other 
end. 

When  a  tube  is  in  service  for  the  first  time,  to 
insure  complete  removal  of  any  organic  matter 
that  might  be  clinging  to  the  glass  or  the  copper 
oxide,  the  fine  oxide  is  used  unmixed  with  any  other 
substance,  and  the  whole  tube  is  heated  for  several 
hours  while  a  stream  of  dry  air  is  passing  through. 
In  this  case  an  ordinary  calcium  chloride  tube  takes 
the  place  of  the  absorption  apparatus.  If  moisture 
has  collected  in  the  tube  toward  the  end,  it  must 
be  removed  by  warming  the  tube  at  that  point.  A 
stream  of  air  can  be  used  for  the  combustion  proc- 
ess. Pure  oxygen,  however,  is  very  much  better 
for  substances  that  do  not  oxidize  readily,  because 
of  the  rapidity  and  completeness  of  combustion 
in  its  presence.  With  oxygen,  completion  of  the 
process  is  indicated  when  the  outgoing  stream  from 
the  absorption  apparatus  causes  an  ember  on  the 
end  of  a  splinter  of  wood  to  glow  brightly. 

It  may  add  to  the  understanding  of  the  process  to 
trace  the  air  or  oxygen  stream  through  the  whole 


ELEMENTARY  ANALYSIS 


31 


apparatus  (see  Fig.  11).  It  first  bubbles  through  a 
strong  solution  of  caustic  potash,  which  removes 
most  of  the  carbon  dioxide;  then  passes  through  a 
large  U-tube  or  drying-tower  containing  soda- 
lime  or  small  pieces  of  NaOH,  which  removes  the 
last  traces  of  carbon  dioxide;  then  through  another 
U-tube  containing  calcium  chloride,  which  removes 


FIG.  12. 

moisture.1  The  dry  gas  passes  into  the  combustion- 
tube;  when  it  reaches  the  fine  copper  oxide  it  aids 
the  oxidation  of  the  organic  substances,  and  carries 
along  with  it  the  carbon  dioxide  and  steam  pro- 
duced, also  any  volatilized  material  that  has  not 

lfro  insure  thorough  drying  the  air  is  sometimes  finally 
bubbled  through  sulphuric  acid.  In  this  case  H2S04  must  also 
be  used  as  the  absorbent  in  the  place  of  the  calcium  chloride 
tubes  (see  Fig.  12). 


32  ORGANIC  CHEMISTRY 

been  oxidized,  and  brings  them  into  contact  with 
the  coarse  copper  oxide,  which  completes  the  oxida- 
tion; thus  the  stream  when  it  reaches  the  end  of 
the  tube  consists  of  air  or  oxygen  containing  car- 
bon dioxide  and  water- vapor.  In  passing  through 
the  calcium  chloride  tube  of  the  absorption  appara- 
tus the  water  is  absorbed,  and  finally  in  bubbling 
through  the  caustic  potash  solution  of  the  absorp- 
tion bulbs  the  carbon  dioxide  is  removed;  the  slight 
amount  of  moisture  picked  up  here  is  removed  by 
the  straight  calcium  chloride  tube  (see  Fig.  12). 
The  details  of  the  method  are  given  in  the  following 
experiment. 

EXPERIMENT.     Combustion    analysis    of   salicylic 
acid.    After  the  combustion-tube  has  been  charged 


FIG.  13. 

and  thoroughly  heated  as  directed  above,  remove 
the  stopper  at  the  end  nearest  the  air-tank,  quickly 
pour  out  the  coarse  oxide  into  a  clean  dry  beaker, 
pull  out  the  short  spiral,  and  finally  pour  out  the  fine 
oxide  into  another  beaker  and  replace  the  stopper. 
Put  the  beakers  and  the  spiral  into  a  desiccator. 
Weigh  accurately  a  weighing-bottle  containing  about 
0.2  gm.  of  pure  salicylic  acid  that  has  stood  in  a 
desiccator  several  days.  Through  a  clean  short- 
stemmed  funnel  pour  the  salicylic  acid  into  the  mix- 
ing-tube (see  Fig.  13) ;  add  some  of  the  fine  oxide 
carefully  through  the  funnel  in  such  a  way  that  all 
the  crystals  of  salicylic  acid  are  carried  along  with 


ELEMENTARY  ANALYSIS  33 

the  CuO  into  the  mixing-tube.  When  the  tube  is 
half  full,  insert  the  stopper;  hold  the  tube  and  stop- 
per firmly  and  shake  very  vigorously.  When  well 
mixed,  quickly  empty  the  contents  into  the  com- 
bustion-tube; rinse  the  '  mixing-tube  by  shaking 
successively  with  small  portions  of  fine  oxide  until 
all  the  oxide  has  been  transferred  to  the  combustion- 
tube.  Replace  the  spiral  and  pour  in  the  coarse 
oxide.  Replace  the  stopper,  connect  with  the  air- 
purifying  apparatus,  and  start  the  air-stream. 
The  CaCl2  tube  remains  at  the  other  end  of  the 
tube.  Reweigh  the  weighing-bottle. 

Begin  lighting  the  burners  at  the  end  near  the  cal- 
cium chloride  tube,  starting  one  burner  at  a  time 
and  with  the  lowest  flame  possible,  then  very  grad- 
ually increasing  the  flames  in  number  and  size. 
Do  not  heat  near  the  fine  oxide.  In  the  meantime 
weigh  the  calcium  chloride  absorption-tube  and 
the  caustic  potash  bulb  with  its  calcium  chloride 
tube  (remove  the  plugs  before  weighing),  and 
attach  them  in  place  of  the  ordinary  calcium 
chloride  tube.  When  the  coarse  oxide  has  been 
brought  to  a  dull  red  heat,  the  part  of  the  tube  that 
contains  this  having  been  covered  with  tiles,  start 
the  heating  of  the  other  end  of  the  tube,  very  grad- 
ually, beginning  at  the  far  end.  Stop  the  air-stream. 
When  the  fine  oxide  is  heated,  watch  closely,  and 
turn  down  the  burners  here  if  bubbles  pass  too 
rapidly  through  the  potash  bulbs.  The  bubbles 
should  not  go  so  fast  that  they  cannot  be  easily 
counted  (three  in  two  seconds).  Finally,  bring  the 
whole  tube  to  a  dull  red  heat  (never  hotter).  When 


34  ORGANIC  CHEMISTRY 

bubbles  cease  to  pass,  combustion  is  practically 
complete;  but  continue  the  heating  of  the  tube 
for  thirty  minutes  (fifteen  if  oxygen  is  used)  while 
passing  a  slow  air-stream  (which  will  give  the  proper 
rate  of  bubbles).  Then  begin  to  cool  the  tube  by 
gradually  turning  down  the  burners  from  each  end, 
but  do  not  remove  the  tiles.  Examine  the  end 
of  the  combustion  tube  for  condensed  water;  if 
present,  vaporize  it  by  careful  heating  at  that  point. 
If  oxygen  is  used,  change  to  an  air-stream  at  this 
point  so  as  to  clear  oxygen  out  of  the  absorption 
tubes  before  reweighing.  During  the  first  fifteen 
minutes  of  cooling  pass  the  air-stream  more  rapidly 
to  sweep  out  of  the  tube  all  water- vapor  and  carbon 
dioxide.  Disconnect  the  absorption  tubes,  put  on 
the  plugs,  and  allow  to  cool  in  the  balance  room 
for  one  hour.  When  cool,  reweigh  after  removing 
the  plugs.  Do  not  forget  to  attach  the  calcium 
chloride  tube  in  the  place  of  the  absorption  appara- 
tus. Before  the  combustion-tube  is  used  for  another 
analysis,  it  should  be  heated  for  an  hour  while  dry 
air  is  passed  through  it.  The  KOH  solution  in 
the  potash  bulbs  should  not  be  used  for  more  than 
two  combustions. 

The  increase  in  weight  of  the  U  calcium  chloride 
tube  indicates  the  weight  of  the  water  produced  by 
the  combustion.  One-ninth  of  this  is  hydrogen; 
therefore  the  per  cent  of  hydrogen  present  in  the 
substance  burned  can  be  obtained  by  the  following 
formula : 

wt.  of  H20  produced  X 100 


Per  cent  H 


9  Xwt.  of  substance  burned* 


ELEMENTARY  ANALYSIS  35 

The  increase  in  weight  of  the  potash  bulb  and 
straight  calcium  chloride  tube  is  equal  to  t'he  weight 
of  the  carbon  dioxide  produced.  Carbon  represents 
TT  of  this;  therefore  for  calculating  the  per  cent  of 
carbon  the  formula  used  is: 

,  ~     wt.  of  C02  produced  X3  X 100 
Per  cent  C=  —  — . 

11  Xwt.  of  substance  burned 

The  sum  of  the  per  cents  of  hydrogen  and  carbon 
deducted  from  100  gives  the  per  cent  of  oxygen. 

If  the  substance  contains  nitrogen,  oxides  of  nitro- 
gen may  be  formed  when  the  substance  is  oxidized 
as  above.  This  necessitates  a  special  modification 
of  the  method,  because  these  oxides  are  absorbed 
by  caustic  potash.  A  long  copper  spiral  (12-15 
cm.),  which  has  been  reduced  to  pure  copper  by 
dipping  it  while  hot  into  alcohol,1  is  put  into  the  end 
of  the  tube  nearest  the  weighed  absorption  apparatus 
in  the  place  of  part  of  the  coarse  oxide.  When  the 
nitrogen  oxides  come  in  contact  with  the  hot 
reduced  copper,  they  are  deprived  of  their  oxygen 
by  the  copper,  and  nitrogen  is  set  free. 

Of  course  a  free  stream  of  air  or  oxygen  cannot  be 
used  in  this  case  until  combustion  is  complete, 
otherwise  the  reduced  copper  spiral  would  become 
oxidized  and  be  rendered  useless.  The  air-stream 
is  used  to  clear  carbon  dioxide  out  of  the  tube  at 
the  start  before  the  heat  is  applied  to  the  reduced 
copper  spiral;  during  combustion  the  air  is  shut 

1  By  this  treatment  any  oxide  adherent  to  the  copper  yields 
up  its  oxygen  to  oxidize  the  alcohol  to  aldehyde. 


36  ORGANIC  CHEMISTRY 

off;  when  combustion  is  complete  the  air-stream  is 
again  turned  on  to  remove  all  the  products  from  the 
tube. 

//  halogens  are  present  in  the  substance  to  be 
analyzed  a  silver  spiral  must  be  used  in  place  of 
the  reduced  copper  spiral.  The  silver  combines 
with  the  halogens  and  prevents  their  passing  into 
the  absorption  tubes,  where  they  would  be  absorbed. 

When  -  sulphur  or  phosphorus  is  present  lead 
chromate  takes  the  place  of  the  cupric  oxide  in  the 
tube.  The  sulphur  or  phosphorus  is  fully  oxidized, 
and  is  held  in  the  tube  as  sulphate  or  phosphate  of 
lead. 

To  estimate  the  nitrogen  alone  in  an  organic  sub- 
stance the  same  tube  as  that  described  above  for 
nitrogenous  substances  can  be  employed,  provided 
a  stream  of  dried  carbon  dioxide  gas,  instead  of  air, 
is  used  for  removing  the  gases,  etc.,  produced  by  the 
combustion  and  for  clearing  out  the  nitrogen  and 
oxygen  contained  in  the  tube  before  the  heating  is 
begun.  The  absorption  apparatus  in  this  case  is  a 
gas  burette  (a  burette  closed  with  a  glass  cock  at 
the  top)  having  some  mercury  in  the  bottom  to 
act  as  a  valve,  and  filled  with  a  40%  solution  of 
caustic  potash  (see  Fig.  14).  When  bubbles  no 
longer  collect  at  the  top  of  the  burette  and  the  latter 
remains  full  of  caustic  (i.e.,  when  only  carbon 
dioxide  is  passing  out  of  the  tube) ,  the  carbon  dioxide 
is  shut  off  and  combustion  is  carried  out  by  heating 
the  tube  gradually  up  to  a  red  heat.  When  com- 
bustion is  completed  carbon  dioxide  is  passed  again 
until  the  tube  is  cleared  of  nitrogen,  as  shown  by 


ELEMENTARY  ANALYSIS 


37 


the  constancy  of  the  volume  of  the  gas  in  the 
burette.  The  caustic  potash  absorbs  all  the  pro- 
ducts of  combustion  except  nitrogen.  The  burette 
is  allowed  to  stand  for  an  hour  to  come  to  room 
temperature,  the  alkali  being  leveled  up  in  the  appa- 
ratus. The  caustic  potash 
in  the  reservoir  is  brought 
to  exactly  the  same  level  as 
that  in  the  burette,  and 
the  number  of  cubic  centi- 
meters of  gas  is  read  off. 
The  temperature  of  the  ni- 
trogen is  found  by  placing 
a  thermometer  against  the 
burette,  with  the  bulb  at 
the  mid-level  of  the  gas. 
The  barometric  reading 
(corrected  for  temperature) 
must  also  be  taken.  The 
results  of  the  analysis  are 
then  computed  by  referring 
to  specially  prepared  tables, 
which  give  in  grams  the 
amount  of  nitrogen  corre- 
sponding to  1  c.c.  of  the  moist  gas  in  the  burette, 
at  various  temperatures  and  under  various  pressures 
(see  Appendix,  p.  447).  In  order  to  use  the  table 
for  nitrogen  collected  over  alkali,  add  to  the  baro- 
metric pressure  the  difference  between  the  vapor 
pressure  of  water  and  that  of  40%  potassium 
hydroxide  at  the  temperature  of  observation  (see 
Table  VI,  p.  450). 


FIG.  14. 


38  ORGANIC  CHEMISTRY 

An  easier  method  of  nitrogen  estimation  is  the 
Kjeldahl  method,  by  which  the  nitrogen  in  the  organic 
substance  is  converted  into  ammonia  by  heating 
with  pure  sulphuric  acid.  The  ammonium  sulphate 
produced  can  then  be  treated  with  alkali,  and  the 
ammonia  thus  liberated  distilled  into  a  measured 
quantity  of  standard  acid.  From  the  amount  of 
this  latter  which  is  thus  neutralized,  the  amount  of 
nitrogen  contained  in  the  organic  substance  can 
readily  be  calculated.  A  few  organic  compounds 
do  not  give  a  correct  nitrogen  estimation  by  the 
Kjeldahl  method.  This  method  is  extensively 
employed  in  biochemical  analysis  and  will  be  found 
fully  described  in  many  of  the  laboratory  manuals 
on  that  subject. 

Oxygen  is  not  estimated  directly,  but  is  calculated 
by  deducting  from  one  hundred  the  sum  of  the  per 
cents  of  all  the  other  elements  present. 

After  the  percentage  composition  is  determined,  a 
provisional  formula  for  the  compound  may  be  found 
as  follows:  divide  the  percentage  number  of  each 
element  by  its  atomic  weight,  divide  each  of  the 
resulting  figures  by  the  smallest  of  them  (as  the 
greatest  common  divisor  *),  and  make  use  of  these 
smaller  figures,  or  the  nearest  whole  number,  to 
express  the  number  of  atoms  of  each  element  in 
one  molecule.  The  following  example  will  illus- 
trate this.  Alcohol  was  found  by  one  analysis 
to  contain  52.05%  C,  13.13%  H,  and  34.82%  O. 
Then 

JIn  many  cases  some  other  common  divisor  will  have  to 
be  used. 


ELEMENTARY  ANALYSIS  39 

i 

C  52.05-12=  4.337;  4.337-^-2.176=1.993 
H  13.13-  1=13.130;  13.130^2.176=6.030 
O  34.82-16=  2.176;  2.176*2.176  =  1.000 

Therefore  the  formula  may  be  C2H60.  The  same 
percentage  composition  would,  however,  be  shown  by 
any  substance  having  the  formula  C2nH6nOn.  It 
becomes  necessary  then  to  determine  the  number 
of  atoms  in  the  molecule  by  finding  out  the  molecular 
weight;  the  value  of  n  is  thus  discovered,  so  that  it 
becomes  possible  to  write  the  correct  empirical 
formula, 


CHAPTER   IV 

MOLECULAR  WEIGHT  DETERMINATION.  THE  NA- 
TURE OF  SOLUTIONS.  OSMOTIC  PRESSURE. 
IONIZATION.  SURFACE  TENSION.  VISCOSITY. 
COLLOIDAL  SOLUTIONS 

MOLECULAR  WEIGHT  DETERMINATION  BY  ANALYSIS 
OF  DERIVATIVES 

THE  molecular  weight  of  a  substance  can  be 
deduced  from  a  quantitative  analysis  of  its  deriva- 
tives. This  method  is  most  easily  applied  to  acids 
and  bases.  Take,  for  example,  a  simple  acid,  such 
as  acetic.  By  analysis,  its  formula  might  be  CH2O, 
or  any  multiple  thereof.  By  forming  its  silver  salt 
and  estimating  the  amount  of  silver  in  it,  this  will  be 
found  to  be  64.6%.  Now,  knowing  that  the  atomic 
weight  of  silver  is  107.9  and  that  it  is  monovalent, 
and  having  ascertained  that  only  one  silver  acetate 
occurs  (showing  that  the  acid  is  monobasic),  we  can 
see  what  formula  agrees  with  this  proportion  of  silver 
in  silver  acetate.  Suppose  this  salt  to  have  the 
formula  CHOAg,  then  the  per  cent  of  Ag  must  be 

-X 100  =78.8.     Obviously  CH2O  cannot  be  the 

136.9 

correct  formula  for  acetic  acid.  If  we  take  C2H3O2Ag 
as   the   formula,    the   per   cent   of   silver   will   be 

— ^  X 100  =  64.6% ;  therefore  C2H4O2  is  the  correct 
166.9 

40 


MOLECULAR  WEIGHT  DETERMINATION          41 

formula.  In  the  case  of  bases,  their  chlorplatinates 
have  been  found  to  be  the  most  suitable  compounds 
to  form  for  this  purpose. 

MOLECULAR  WEIGHT  .OF  GASES  AND  VAPORS 

In  order  to  understand  fully  the  physico-chemical 
nature  of  solutions  and  the  subject  of  molecular 
weight  determinations,  it  will  be  advisable  briefly 
to  review  some  of  the  fundamental  points  in  chem- 
istry that  relate  to  these  subjects.  As  we  shall  see 
later,  gases  and  solutions  in  their  physico-chemical 
behavior  are  very  much  alike,  so  that  a  clear  con- 
ception of  the  gas  laws,  which  are  well  known  and 
readily  tested,  will  enable  us  to  study  more  satis- 
factorily the  nature  of  solutions. 

The  three  important  gas  laws  are  as  follows: 

1.  Gay-Lussac's   or   Dalton's    law:    provided   its 
pressure  remains  unchanged,  every  gas  expands  by 
-2^3  of  its  volume  at  0°  for  each  degree  of  rise  of  tem- 
perature. 

Thus  a  gas  occupying  a  volume  of  1  liter  at  0° 
will  occupy  2  liters  at  273°,  if  the  pressure  remains 
constant.  In  making  calculations  it  should  be 
remembered  that  the  absolute  temperature  of  0°  is 
273°,  and  therefore  for  any  temperature  above  0° 
the  absolute  temperature  is  that  temperature  plus 
273°.  Another  way  of  stating  the  law  is  that  the 
volume  of  a  gas  (at  constant  pressure)  varies  directly 
with  its  absolute  temperature. 

2.  Boyle's    law:    provided    the    temperature   re- 
mains constant,  the  volume  of  a  gas  varies  inversely 
as  the  pressure.     Thus,  if  1  liter  of  gas  be  compressed 


42  ORGANIC  CHEMISTRY 

into  the  space  of  0.5  liter,  the  pressure  has  been 
doubled. 

3.  Avogadro's  hypothesis:  under  the  same  con- 
ditions of  temperature  and  pressure,  equal  volumes 
of  all  gases  contain  the  same  number  of  molecules. 

The  relative  weights  of  equal  volumes  of  different 
gases,  under  the  same  conditions  of  temperature  and 
pressure,  must  represent  the  relative  weights  of  the 
molecules  (Avogadro's  hypothesis).  If,  then,  we 
take  the  weight  of  one  gas  as  the  standard,  the 
molecular  weights  of  other  gases  can  readily  be 
ascertained.  Hydrogen  is  the  gas  thus  chosen, 
and  since  its  molecule  contains  two  atoms,  we 
ascribe  to  it  a  molecular  weight  of  2.  Similarly, 
oxygen  has  a  molecular  weight  of  32,  being  sixteen 
times  heavier  than  hydrogen.  Two  grams  of  hydro- 
gen at  0°  and  760  mm.  Hg  pressure  has  a  volume 
of  22.4  liters.  But  2  is  the  molecular  weight  of 
hydrogen;  therefore  if  we  take  the  number  of 
grams  of  any  other  gas  equivalent  to  its  molecular 
weight  this  amount  of  gas  will  also  occupy  a  volume 
of  22.4  liters  (at  0°  and  760  mm.).  Such  a  weight 
in  grams  corresponding  to  the  figures  for  the  molec- 
ular weight  is  called  a  gram-molecule  or  a  mole.  In 
consequence  of  Boyle's  law  it  must  follow  that  if 
we  compress  a  mole  of  any  gas  at  0°  to  the  volume 
of  1  liter,  it  will  have  a  pressure  of  22.4  atmospheres 
(i.e.,  22.4x760  mm.  Hg). 

If,  therefore,  we  know  the  volume,  temperature, 
and  pressure  of  a  known  weight  of  a  gas,  it  is  easy 
by  applying  the  above  laws  to  determine  its  molec- 
ular weight.  As  an  example,  suppose  that  0.2 


MOLECULAR  WEIGHT  DETERMINATION          43 

gm.  of  a  dry  gas  has  a  volume  of  50  c.c.  at  10°  and 
740  mm.  Hg;  what  is  the  molecular  weight? 


070 

50  X—  —  X~  =46.899  -c.c  at  0°  and  760  mm. 
273  -f-  10    760 

But  a  mole  occupies  22,400  c.c.     Then  0.2  gm.  is 

46.899 

'       of  a  mole,  therefore  the  mole  is  95.4  gm.     The 


molecular  weight  is  95.4. 

Vapors  obey  the  same  laws  as  gases.  Substances, 
solid  or  liquid,  that  can  be  vaporized  by  heat  sub- 
mit to  a  molecular  weight  determination  as  readily 
as  gases.  In  practice  the  determination  is  made 
either  by  weighing  a  known  volume  of  the  substance 
in  the  form  of  vapor,  or  by  measuring  the  volume 
of  the  vapor  produced  from  a  known  weight  of  the 
substance. 

A  known  volume  of  vapor  is  weighed  when  Dumas' 
method  is  used.  By  this  method  an  indefinite 
quantity  of  the  substance  is  vaporized  in  a  flask- 
like  bulb  by  heating  the  bulb  in  an  oil-bath.  The 
neck  of  this  flask-like  bulb  is  drawn  out  to  a  fine 
tip.  When  all  the  air  is  displaced  from  the  bulb, 
and  the  substance  is  completely  vaporized,  the  tip  is 
sealed  off  in  a  flame.  The  temperature  of  the  bath 
is  recorded,  also  the  barometric  pressure.  After 
cooling,  the  weight  of  the  substance  in  the  bulb 
and  the  capacity  of  the  latter  are  accurately  deter- 
mined, and  from  these  data  the  molecular  weight 
can  be  calculated.  This  method,  while  simple  in 
principle,  is  nevertheless  tedious  in  practice. 


44  ORGANIC  CHEMISTRY 

A  much  more  useful  method  for  general  purposes 
is  that  of  Victor  Meyer,  in  which  the  volume  of  a 
known  weight  of  vapor  is  ascertained  by  finding 
how  much  air  is  displaced  in  a  closed  apparatus 
when  the  substance  changes  to  a  vapor. 

The  apparatus/  as  shown  in  the  figure,  consists 
of  an  elongated  bulb  continued  above  into  a  long 
neck  closed  at  the  top  by  a  rubber  stopper;  from 
the  neck  passes  a  side  tube,  which  is  connected  by 
heavy  rubber  tubing  with  a  gas  burette.  The  bulb 
is  suspended  in  a  wide  tube  having  a  bulb-like 
expansion  at  its  closed  end  (the  upper  two-thirds  of 
this  tube  should  be  wrapped  with  asbestos  paper) 
and  containing  some  liquid  with  a  boiling-point 
40°-50°  above  the  vaporization  temperature  of 
the  substance. 

EXPERIMENT.  Fill  the  bulb  of  the  outer  tube 
two-thirds  full  of  distilled  water;  suspend  the  inner 
tube  in  it  by  means  of  a  cork  (this  will  have  to  be 
cut  in  two  and  then  wired  together  again).  By 
means  of  this  cork  also  hang  a  thermometer  in  the 
steam-chamber  and  insert  a  bent  glass  tube  as  a 
steam- vent.  Now  boil  the  water  (start  the  heating 
very  gradually).  When  the  thermometer  registers 
a  constant  temperature,  i.e.,  the  boiling-point  of 

1  An  excellent  modification  of  this  apparatus  has  been 
made  by  Bleier  and  Kohn,  by  which,  instead  of  measuring 
air-displacement,  the  increase  of  pressure  (the  volume  of  gas 
in  the  apparatus  being  constant)  due  to  the  vaporization  is 
measured  by  means  of  a  mercury  manometer.  Before  making 
an  estimation  the  air-pressure  in  the  apparatus  is  lowered  by 
a  suction-pump. 


MOLECULAR  WEIGHT  DETERMINATION 


45 


the  water,1  connect  the  side  tube  with  the  gas 
burette  and  cork  the  inner  tube  tightly  with  a  rubber 
stopper.  Bring  the  water  in  the  burette  and  in  the 
reservoir  to  exactly  the  same  level.  If  there  is  no 
variation  from  this  level  for  5-10  minutes,  the 
apparatus  is  ready  for  making  an  estimation.  The 
entire  column  of  air  in  the  narrow  tube  has  now 
come  to  the  temperature  of  the  steam  surrounding 
it.  Remove  the  stopper 
of  the  inner  tube  and  place 
in  position  (supported  by 
the  glass  rod,  which  fits 
the  extra  branch  tube  and 
extends  into  the  neck  of 
the  main  tube,  as  shown 
in  Fig.  15)  a  little  sealed 
glass  bulb  containing  a 
known  weight  of  pure 
chloroform  (the  bulb  hav- 
ing been  weighed  before 
and  after  filling).  Fit  the 
stopper  tightly,  and  wait 
a  few  minutes  to  determine  whether  the  volume 
of  the  air  in  the  apparatus  remains  constant  (as 
indicated  by  the  level  of  the  liquid  in  the  burette). 
When  constant,  fill  the  burette  exactly  to  the  cock 
by  raising  the  reservoir  after  having  brought  the 
burette  into  communication  with  the  outer  air  by 
means  of  a  two-way  cock  (either  the  cock  of  the 

1  Boiling-point  at  735  mm.  barometric  pressure  is  99.1°, 
at  740  mm.  99.3°,  at  745  mm.  99.4°,  at  750  mm.  99.6°,  at 
755  mm.  99.8°,  and  at  760  mm.  100°. 


FIG.  15. 


46  ORGANIC  CHEMISTRY 

burette  or  one  specially  inserted  in  the  rubber 
tubing  connection).  Then  close  the  cock,  so  that 
the  burette  communicates  only  with  the  air  of  the 
system.  Now  drop  the  bulb  to  the  bottom  of  the 
Victor  Meyer  tube  by  pulling  the  rod.  Some 
glass  wool  has  been  put  into  the  bottom  of  the 
tube  to  prevent  injury.  Vapor  forms  and  hot 
air  is  pushed  over  into  the  burette.  Level  up  the 
water  in  the  burette  with  that  in  the  reservoir. 
When  the  level  remains  absolutely  constant  for  a 
few  moments,  close  the  cock  of  the  burette.  After 
allowing  sufficient  time  for  cooling,  measure  the 
volume  of  the  air  displaced  into  the  burette  in 
exactly  the  same  way  as  in  nitrogen  estimations 
(see  p.  37),  correcting  for  temperature,  also  for 
aqueous  (see  Appendix)  and  barometric  pressure, 
and  convert  to  the  volume  at  0°  and  760  mm.  (see 
p.  43).  To  make  the  calculation  divide  22,400 
(22.4  L.)  by  the  number  of  cubic  centimeters  of 
air  displaced,  and  multiply  this  quotient  by  the 
weight  of  the  chloroform  vaporized;  the  product 
gives  the  weight  of  a  gram-molecule  of  the  sub- 
stance, and  the  same  figures  express  the  molecular 
weight. 

THE    NATURE    OF    SOLUTIONS.    OSMOTIC    PRESSURE 

In  their  physical  properties  solutions  are  very 
different  from  gases.  In  attempting  to  apply  gas 
laws  to  substances  in  solution,  it  is  evident  that 
other  methods  than  those  used  in  the  case  of  gases 
must  be  adopted  to  measure  the  pressure  of  the  dis- 
solved substance.  We  measure  the  pressure  of  a 


OSMOTIC  PRESSURE  47 

gas  by  means  of  a  manometer,  but  it  is  ob- 
viously impossible  to  measure  the  pressure  of  a 
dissolved  substance  by  the  same  means,  for  the 
only  pressure  which  the  manometer  can  record 
is  that  of  the  solution  against  the  walls  of  its  con- 
tainer. 

By  making  use  of  membranes,  however,  much 
can  be  learned  about  the  behavior  of  solutions.  If 
a  permeable  membrane,  for  example,  parchment 
paper,  is  arranged  as  a  partition  to  separate  a  solu- 
tion of  some  substance  from  pure  solvent,  the  two 
liquids  refuse  to  remain  separate.  The  solvent 
passes  through  the  membrane  in  both  directions; 
but  a  more  important  fact  is  that  the  dissolved 
substance  diffuses  through  the  membrane  into  what 
was  at  the  start  pure  solvent,  and  this  process  con- 
tinues until  the  liquids  on  both  sides  of  the  membrane 
become  solutions  of  the  same  concentration.  The 
energy  manifested  in  this  process  of  dialysis  is 
diffusion  pressure. 

If,  however,  a  much  less  permeable  membrane  is 
used,  diffusion  of  a  solute  through  it  is  prevented; 
but  the  solvent  readily  passes  through  in  both 
directions.  Such  a  membrane  is  called  a  semi- 
permeable  membrane.  In  a  properly  constructed 
apparatus  this  membrane  can  be  used  to  demon- 
strate a  kind  of  pressure  different  from  diffusion 
pressure. 

The  best  example  of  a  semi-permeable  membrane 
is  a  film  of  copper  ferrocyanide.  Since  this  film 
of  copper  ferrocyanide  is  too  fragile  to  exist  un- 
supported, it  may  be  deposited  in  the  pores  of  a 


48  ORGANIC  CHEMISTRY 

porous  cell  (such  as  is  used  for  electric  batteries), 
and  the  following  method  may  be  used  in  prepar- 
ing it. 

A  fine-grained  porous  cell,  about  four  inches 
long  and  one  inch  inside  diameter,  is  closed  with  a 
perforated  rubber  stopper,  through  which  passes 
a  glass  tube  connecting  with  a  suction-pump.  The 
cell  is  set  in  water,  and  the  water  is  sucked  through 
the  pores;  then  placed  in  acid,  then  in  water 
again.  By  this  means  the  pores  of  the  cell  are 
thoroughly  cleaned,  and  air  is  removed.  When 
clean,  the  cell  is  placed  in  a  concentrated  solu- 
tion of  copper  sulphate,  and  suction  is  maintained 
until  the  pores  are  completely  filled.  The  inside 
and  the  outside  of  the  cell  are  then  thoroughly 
washed  with  distilled  water,  after  which  it  is 
filled  with  3%  potassium  ferrocyanide  solution 
and  the  outside  is  exposed  to  a  solution  of  copper 
sulphate.  The  copper  sulphate  reacts  with  the 
potassium  ferrocyanide  in  the  pores  of  the  porous 
pot,  so  that  a  fine  gelatinous  precipitate  of  copper 
ferrocyanide  is  deposited.  After  standing  for  a 
day  the  cell  is  washed  in  water. 

If  a  solution  of  cane  sugar  is  placed  inside  and  the 
cell  is  suspended  in  water,  water  will  pass  into  the 
cell  and  cause  the  volume  of  fluid  in  this  to  increase 
so  that,  by  connecting  a  vertical  glass  tube  with 
the  cell  by  means  of  a  rubber  stopper,  fluid  will 
mount  up  in  it  to  a  very  considerable  height.  If, 
however,  the  liquid  in  the  cell  is  put  under  pressure, 
increase  in  the  volume  of  the  solution  is  prevented. 
When  the  system  is  in  equilibrium  because  the 


OSMOTIC  PRESSUEE 


49 


pressure  is  so  regulated  as  to  prevent  change  in 
volume,  exactly  as  much  solvent  diffuses  out  as 
diffuses  in.  By  connecting  a  manometer  with 
the  apparatus,  the  pressure  can  be  determined 
by  measuring  the  height  of 
the  column  of  mercury.  Large 
pressures  are  reported  as  at- 
mospheres pressure,  760  mm. 
of  mercury  constituting  one 
atmosphere.  The  pressure 
thus  demonstrated  is  called 
osmotic  pressure. 

No  membrane  has  ever  been 
prepared  that  is  absolutely 
semi-permeable,  that  is,  im- 
permeable to  all  solutes.  A 
carefully  prepared  membrane 
is  truly  semi-permeable  to 
sugar  solutions  and  to  col- 
loidal solutions. 

The  law  of  osmotic  pressure 
as  stated  by  van't  Hoff  and 
modified  by  Morse,  is  as  fol- 
lows: The  osmotic  pressure 
of  a  substance  in  dilute  solu- 
tion is  the  same  amount  of 
pressure  that  the  substance  would  exert,  if  it  could 
exist  in  the  form  of  a  gas  at  the  same  tempera- 
ture as  the  solution,  and  if  it  were  confined  to 
the  same  volume  as  that  occupied  by  the  pure 
solvent.  If  this  law  could  be  applied  to  concentrated 
solutions,  it  would  mean  that  the  osmotic  pressure 


FIG.  16. 


50  ORGANIC  CHEMISTRY 

of  all  weight-normal  1  solutions  at  0°  must  be  22.4 
atmospheres,2  because  this  is  the  pressure  of  a 
gram-molecule  of  gas  when  compressed  to  the 
volume  of  a  liter.  On  the  basis  of  this,  we  can 
calculate  what  the  pressure  of  any  dissolved  sub- 
stance in  solution  will  be.  Thus,  the  pressure  x 
of  a  1%  solution  of  cane  sugar  may  be  calculated 
from  the  proportion:  Molecular  solution  :  1% 
solution::  22.  4  atmospheres  :#.  Solutions  which 
obey  the  laws  of  osmotic  pressure  most  accurately 
are  those  that  are  not  more  concentrated  than  one- 
tenth  gram-molecular. 

Since  a  comparison  has  been  made  of  osmotic 
pressure  to  gas  pressure,  it  will  be  of  interest  to 
test  the  application  of  the  gas  laws  to  solutions. 

1.  According  to  Gay-Lussac's  law,  the  osmotic 
pressure  should  be  proportional  to  the  absolute 
temperature.  That  this  is  so  is  proved  by  observa- 
tions like  the  following:  A  1%  solution  of  cane  sugar 
at  14.2°  has  an  osmotic  pressure  of  510  mm.  Hg,  and 
at  32°  of  544  mm.  Hg.  According  to  calculation  it 
should  be  540.6  mm.  Hg  (practically  agreeing  with 
the  finding),  thus 


1  By  gram-molecular  solution  is  meant  the  molecular  weight 
of  a  substance  in  grams  dissolved  in  an  amount  of  solvent 
sufficient  to  make  1  L.  of  solution,  while  by  weight  normal 
is  meant  a  solution  in  which  the  gram-molecular  weight  of  sub- 
stance is  dissolved  in  1000  gm.  of  solvent. 

2  The  pressure  should  be  22.28  atmospheres  according  to 
Morse,  because  1000  gm.  of  water  at  0°  has  a  volume  greater 
than  1000  c.c. 


OSMOTIC  PRESSURE  51 

2.  According  to  Boyle's  law,  the  osmotic  pressure 
should  be  inversely  proportional  to  the  volume  of 
the  solution,  or,  in  other  words,  directly  propor- 
tional to   the   concentration.     The   osmotic   pres- 
sures of  glucose  solutions  of  varying  strengths  (at 
the  same  temperature,  0°),  have  been  found  to  be 
as  follows: 

Gram-molecules  in  Osmotic  Pressure  in 

1000  gm.  Water.  Atmospheres. 

Observed.  Calculated. 

0.1  2.40  2.23 

0.2  4.65  4.45 

0.3  7.01  6.68 

0.4  9.30  8.91 

0.5  11.65  11.14 

It  will  be  noticed  that  the  pressures  observed  are 
almost  proportional  to  concentration.  Thus  the 
pressure  for  the  0.4  molar  solution  is  twice  that 
for  the  0.2,  but  that  for  the  0.2  is  not  quite  twice 
that  for  the  0.1.  The  figures  given  above  as  cal- 
culated pressures  are  the  gas  pressures  which 
the  glucose  would  be  under  if  in  the  form  of  a  gas 
at  0°  and  confined  to  the  same  volume  as  the 
solvent.  These  values  are  a  little  lower  than  the 
actual  osmotic  pressure.  Some  would  explain 
the  variation  as  due  to  hydration  of  the  sugar 
molecules. 

3.  According  to  Avogadro's  hypothesis,  all  equi- 
molecular  solutions    (i.e.,   solutions  in  which  the 
weights  of  the  solutes  in  a  given  quantity  of  solu- 
tion bear  the  same  ratio  to  one  another  as  the 
molecular  weights  of  those  substances)   ought  to 


52  ORGANIC  CHEMISTRY 

have  the  same  osmotic  pressure.     This  has  been 
found  to  be  the  case. 

Osmotic  pressure  is  related  to  vapor  pressure. 
When  a  substance  is  dissolved,  the  vapor  pressure 
of  the  solvent  is  lowered.  This  lowering  of  vapor 
pressure  explains  why  the  freezing-point  of  a  solu- 
tion is  lower,  and  the  boiling-point  higher  than  that 
of  the  pure  solvent.  Increase  of  osmotic  pressure 
is  proportional  to  decrease  of  vapor  pressure,  so  that 
the  osmotic  pressure  of  a  solution  has  been  cal- 
culated from  its  vapor  pressure.  This  was  found 
to  agree  closely  with  the  pressure  that  was  actually 
measured  in  an  osmotic  apparatus. 

The  tendency  of  the  pure  solvent  to  diffuse 
through  a  membrane,  so  as  to  pass  into  the  liquid 
having  a  lower  vapor  pressure,  can  be  seen  more 
clearly  by  considering  the  effect  of  a  difference  of 
vapor  pressure  in  an  experiment  that  does  not 
involve  the  use  of  a  membrane.  Thus  if  pure 
water  is  put  in  one  beaker  and  an  aqueous  solution 
in  another,  and  both  are  set  in  a  jar  that  is  then 
tightly  closed,  vapor  will  pass  off  from  the  water, 
but  will  be  taken  up  from  the  air  of  the  jar  by  the 
liquid  of  lower  vapor  pressure,  that  is,  by  the  solu- 
tion. The  transfer  of  water  from  one  beaker  to 
the  other  is  equivalent  to  distillation.  If  it  were 
possible  to  subject  the  solution  in  the  one  beaker 
to  pressure  without  at  the  same  time  cutting  the 
liquid  off  from  contact  with  the  air  of  the  jar,  and 
also  without  changing  the  pressure  on  the  pure 
water,  the  vapor  pressure  of  the  solution  could  be 
raised  by  the  increasing  hydrostatic  pressure  until 


OSMOTIC  PRESSURE  53 

finally  it  equaled  that  of  the  pure  water;  and  In 
consequence  distillation  would  cease.  It  will  be 
seen,  therefore,  that  pressure  can  be  used  to  bring 
two  liquids  into  equilibrium  with  each  other  as 
regards  vapor  pressure.  •  It  is  not  at  all  improbable 
that  the  equilibrium  brought  about  in  an  osmotic 
apparatus  by  exerting  pressure  on  the  solution  in 
the  cup,  is  due  to  the  establishing  of  an  equilibrium 
of  the  vapor  pressures  of  the  two  liquids. 

One  of  the  recent  theories  as  to  the  method  of  the 
passage  of  the  solvent  through  the  osmotic  mem- 
brane supposes  that  the  solvent  is  in  the  form  of 
a  vapor  while  passing  through  the  capillary  pores 
of  the  membrane.  The  vapor  condenses,  and  is 
taken  up  by  the  solution  on  the  other  side  of 
the  membrane.  According  to  this  theory  the  pores 
do  not  become  wet,  and  the  process  is  simply 
distillation.  If  we  accept  this  theory,  we  have  no 
difficulty  in  understanding  why  the  molecules  of 
the  dissolved  substance  do  not  diffuse  through  the 
pores  of  a  perfect  semi-permeable  membrane. 

The  old-time  theory  that  the  membrane  acts  as 
a  sieve,  preventing  the  molecules  of  the  solute  from 
passing  through  the  pores,  is  no  longer  tenable. 
It  has  been  recently  shown  that  an  osmotic  mem- 
brane can  be  prepared  by  partially  blocking  the 
pores  of  an  unglazed  porcelain  plate  by  means  of 
a  fine  non-gelatinous  precipitate.  When  the  diam- 
eter of  the  capillaries  has  been  reduced  to  about 
O.SM,  the  plate  can  be  used  to  demonstrate  osmotic 
pressure  (but  the  pressure  will  be  only  a  fraction 
of  the  true  osmotic  pressure  of  a  solution).  But 


54  ORGANIC  CHEMISTRY 

the  diameter  of  these  capillaries  is  from  500  to 
1000  times  the  diameter  of  the  molecules  of  most 
solutes,  so  that  it  is  evident  that  there  is  no  sieve- 
like  action  involved. 

A  theory  that  is  favored  by  some  supposes  that 
the  solvent  passes  through  the  membrane  by  first 
.dissolving  in  the  substance  of  the  membrane  and 
then  passing  out  of  the  membrane  on  the  other 
side.  This  theory  does  not  take  those  membranes 
into  account  that  are  known  to  have  capillary  pores. 
By  using  a  non-porous  membrane,  as,  for  example, 
a  rubber  membrane,  and  by  using  solvents  that  dis- 
solve in  rubber,  the  osmotic  pressure  of  solutions 
made  with  such  solvents  can  be  demonstrated. 
Such  an  experiment  does  not  prove  anything  what- 
ever about  the  mode  of  action  of  a  membrane  in 
the  case  of  aqueous  solutions.  It  may  well  be 
true  that  osmosis  occurs  through  some  membranes 
in  accordance  with  this  solution  theory;  but  the 
theory  certainly  does  not  apply  to  all  membranes. 

Biological  Methods  for  Measuring  Osmotic  Pressure.  If, 
in  the  experiment  with  cane  sugar  solution,  instead  of  placing 
the  cell  in  water  we  had  placed  it  in  a  solution  of  cane  sugar 
weaker  than  that  contained  in  the  cell,  then  the  osmotic  pressure 
would  not  be  so  great  as  in  the  previous  case,  because  water 
would  pass  into  the  cell  only  until  the  strength  of  the  solution 
came  to  be  the  same  as  that  outside  it.  This  fact  leads  us  to 
an  important  conclusion,  viz.:  that  the  relative  strengths  of 
two  solutions  can  be  ascertained  by  seeing  whether  osmosis  oc- 
curs between  them  when  they  are  separated  from  each  other 
by  a  semi-permeable  membrane.1 

1  This  is  true  only  for  solutions  of  diffusible  substances  in  the 
same  solvent  (water). 


OSMOTIC  PRESSURE  55 

In  the  case  of  the  copper  ferrocyanide  cell  above  described, 
we  could  determine  this  fact  by  measuring  the  pressure  inside 
the  cell.  If,  however,  we  employed  a  closed  sac  of  some  semi- 
permeable  membrane  filled  with  one  of  the  fluids,  then  we 
could,  by  suspending  this  sac  in  some  other  fluid,  tell  if  osmosis 
had  occurred,  by  seeing  whether  the  sac  became  distended 
or  the  reverse.  In  the  case  of  the  red  blood-corpuscles  we 
have  a  structure  analogous  to  this.  The  envelope  of  the  cor- 
puscles acts  like  a  semi-permeable  membrane;  it  allows  water 
to  diffuse  through  it,  but  not  salts.1 

Now  a  corpuscle  contains  a  solution  of  salts  and  haemo- 
globin, and  if  it  be  placed  in  a  fluid  containing  in  solution  the 
same  number  of  molecules  as  is  contained  in  the  fluid  inside 
the  corpuscle,  then  no  osmosis  will  occur  in  either  direction 
and  the  corpuscle  will  remain  unchanged  in  volume  Such 
a  fluid  which  is  isosmotic  with  the  fluid  inside  the  corpuscle, 
is  called  an  isotonic  solution.  If  the  corpuscle  be  placed  in 
a  solution  which  is  weaker  than  that  contained  in  the  cor- 
puscle, then  water  will  diffuse  in  and  the  corpuscle  will  distend 
and  may  ultimately  burst.  Such  a  solution  is  said  to  be  hypo- 
tonic.  If  the  corpuscle  be  placed  in  a  solution  which  is  stronger 
than  that  of  its  fluid  contents,  then  water  will  diffuse  out  of 
the  corpuscle,  so  that  the  corpuscle  will  shrink.  Such  a  solution 
is  called  hypertonic. 

This  change  in  the  volume  of  the  corpuscle  may  be  observed 
under  the  microscope,  and  a  quantitative  expression  also  of 
the  change  in  volume  of  the  corpuscle  may  be  obtained  by 
using  an  instrument  called  a  hsematocrit.  This  consists  of 
a  graduated  narrow  capillary  tube,  about  seven  centimeters 
long.  At  one  end  the  tube  is  widened  so  as  to  give  space 
in  which  the  fluids  may  be  mixed.  Blood  is  drawn  into  the 
capillary  by  means  of  a  syringe,  and  its  volume  accurately 
measured.  The  pipette  is  then  closed  at  each  end  by  small, 

1  The  corpuscles  are,  however,  permeable  for  alcohols,  free 
acids,  and  alkalies,  ammonium  salts,  and  urea.  This  explains 
why  an  isotonic  NaCl  solution  remains  isotonic  after  the  addi- 
tion to  it  of  urea,  in  spite  of  the  increase  in  osmotic  pressure. 


56  ORGANIC  CHEMISTRY 

accurately  fitting,  metal  plates  held  in  position  by  a  spring. 
The  tube  is  then  placed  horizontally  in  a  rapid  centrifuge  and 
rotated  so  that  the  corpuscles  are  thrown  to  the  outer  end. 
The  graduation  mark  at  which  the  column  of  corpuscles  stands 
is  then  noted. 

In  another  tube  a  drop  of  the  same  blood  is  mixed  with 
an  equal  volume  of  the  fluid  the  molecular  concentration  of 
which  it  is  desired  to  determine.  The  exact  amount  of  blood 
and  fluid  taken  is  read  off  from  the  graduations  of  the  tube. 
The  two  fluids  are  then  sucked  into  the  wide  part  of  the  tube  and 
mixed  by  means  of  a  fine  platinum  wire.  The  tube  is  then 
closed  and  centrifuged.  If  the  corpuscles  stand  at  the  same 
level  as  for  blood  alone,  then  we  know  that  the  solution  is 
isotonic  with  the  blood-corpuscles,  which  means  that  they 
must  also  be  isotonic  with  the  plasma.  If  the  column  of  cor- 
puscles be  longer,  then  we  know  that  their  volume  must  have 
been  increased,  and  that  the  fluid  under  examination  is  hypo- 
tonic.  If  the  column  of  corpuscles  be  shorter,  the  solution 
is  hypertonic. 

Isosmotic  solutions  are  isotonic  to  the  same  cells 
provided  the  cells  are  impermeable  to  the  solutes. 
Solutions  of  corresponding  concentration  (as,  one- 
tenth  gram-molecular)  of  most  organic  compounds 
(except  metallic  salts,  acids  and  bases)  are  isosmotic. 
Solutions  of  ionizable  substances  (p.  65)  have 
a  greater  osmotic  pressure  than  solutions  of 
other  substances,  since  each  ion  has  the  same 
effect  as  a  molecule;  a  comparison  is  made  in  the 
following : 

Cane  sugar  (not  ionized) 1 . 00 

Potassium  nitrate 1 . 67 

Sodium  chloride 1 . 69 

Calcium  chloride .  .  . .  2 . 40 


OSMOTIC  PPESSURE  57 

These  figures  are  the  isotonic  coefficients  of  the 
substances.  The  coefficient  1.69  for  NaCl  means 
that  a  0.1  gram-molecular  solution  of  salt  has  the 
same  osmotic  pressure  as  a  0.169  gram-molecular 
solution  of  sugar. 

In  the  case  of  living  cells  it  seems  to  be  necessary 
to  take  into  account  selective  permeability;  for 
example,  the  tadpole  when  immersed  in  a  hyper- 
tonic  sucrose  solution  (as  8%)  shrinks  noticeably 
in  twenty-four  hours,  there  being  no  injury  to  the 
epithelium;  on  the  other  hand,  a  tadpole  placed 
in  hypotonic  sucrose  solution  (3%)  does  not  swell 
up,  because  the  epithelial  cells  are  not  noticeably 
permeable  to  water  passing  in. 

EXPERIMENTS.  (1)  Osmotic  Pressure  Effects  in  a 
Vegetable  Membrane.  With  a  sharp  razor  shave 
thin  slices  from  a  red  beet,  mount  some  on  a  slide, 
and  examine  microscopically.  Now  add  a  drop 
of  saturated  NaCl  on  the  slice  and  observe  that  the 
red  substance  shrinks  away  from  the  wall  of  the  cell, 
the  hypertonic  solution  having  caused  plasmolysis. 

(2)  Osmotic  Pressure  Shown  by  an  Animal 
Membrane.  The  large  end  of  an  egg  contains  an 
air  space,  open  the  shell  at  this  point,  removing  it 
down  to  where  the  egg  membrane  joins  the  shell. 
Cross  three  strips  of  parchment  paper  five  inches 
long  over  the  membrane,  and  stretch  them  on  to 
the  shell;  bind  them  down  to  the  shell  beyond 
the  middle  of  the  egg  with  a  rubber  band,  bend 
the  strips  back  on  themselves  and  hold  them  fast 
with  another  rubber  band.  Coat  the  bands  with 


58  ORGANIC  CHEMISTRY 

melted  paraffin  to  keep  them  in  position.  The 
parchment  gives  support  to  the  membrane.  To 
the  opposite  end  of  the  egg  attach  a  small  upright 
glass  tube  by  applying  melted  paraffin,  run  a  long 
needle  down  the  tube  and  carefully  drill  a  hole 
through  the  shell  and  egg  membrane;  or  the  shell 
may  be  nicked  before  fastening  the  tube  in  position, 
and  a  wire  can  be  put  down  the  tube  to  break  the 
egg  membrane.  Immerse  the  egg  in  distilled 
water.  After  standing  some  time  the  egg  contents 
will  have  swollen  sufficiently  to  force  egg  white  up 
into  the  tube. 

(3)  Osmotic  Pressure  Shown  by  an  Inorganic  Mem- 
brane, (a)  Select  a  long  narrow  crystal  of  CuS04, 
tie  a  thread  about  the  middle,  and  fasten  the  thread 
to  a  glass  rod  lying  across  the  top  of  a  small  beaker 
so  that  the  crystal  hangs  in  potassium  ferrocyanide 
solution.  A  copper  ferrocyanide  membrane  forms, 
which  becomes  distended  by  the  passage  of  water 
through  it  toward  the  copper  sulphate. 

(6)  Fill  the  bent  portion  of  a  U-tube  with  melted 
agar  solution,  cool,  and  when  solidified  fill  one  limb 
with  CuS04  solution,  the  other  with  potassium 
ferrocyanide  solution.  On  standing  several  days 
a  sharply  defined  area  of  copper  ferrocyanide 
forms  midway  in  the  agar. 

(c)  Drop  a  small  lump  of  CaC^  into  a  test-tube 
half  filled  with  saturated  potassium  carbonate 
solution.  On  standing  a  membrane  develops  and 
grows,  making  plant-like  forms. 


MOLECULAR  WEIGHT  DETERMINATION  59 

MOLECULAR  WEIGHT  OF  SUBSTANCES  IN  SOLUTION 

Theoretically,  the  measurement  of  the  osmotic 
pressure  would  be  a  simple  enough  way  of  deter- 
mining the  molecular  weight,  but,  in  practice,  the 
method  can  seldom  be  used. 

Is  there  then  no  easily  measurable  physical 
property  of  solutions  which  depends  on  their  molec- 
ular concentration,  and  which  will,  therefore, 
bear  a  relationship  to  the  osmotic  pressure?  The 
vapor  pressure  of  a  solution  is  proportional  to  its 
osmotic  pressure,  but  the  method  of  determining 
vapor  pressure  is  a  difficult  one  to  carry  out.  It 
has  been  found  that  the  temperature  at  which  a 
solvent  freezes  is  lowered  when  a  substance  is 
dissolved  in  it,  and  that  the  amount  of  this  lower- 
ing, or  depression  of  freezing-point,1  is  for  dilute 
solutions  proportional,  not,  in  general,  to  the  chem- 
ical nature  of  the  substance,  but  to  the  number  of 
molecules  of  substance  dissolved  in  a  given  volume. 
(The  same  holds  true  for  the  elevation  of  boiling- 
point,  which  can  be  most  easily  demonstrated  with 
the  McCoy  apparatus.  This  method,  however, 
will  not  be  described  here.)  This  being  so,  it  follows 
that  all  gram-molecular  solutions  in  the  same 
solvent  must  lower  the  freezing-point  to  an  equal 
extent.  The  depression  of  freezing-point  pro- 
duced by  a  gram-molecular  quantity  of  a  sub- 
stance dissolved  in  1000  gm.  of  the  solvent 
(weight  normal  solution)  varies  for  different  sol- 
vents : 

1  Cryoscopy  is  a  name  given  to  freezing-point  determination. 


60  ORGANIC  CHEMISTRY 

Depression  of 
Freezing-point. 

For  water 1.86° 

"    benzol 5.00° 

"    phenol 7.20° 

'"    acetic  acid 3.90° 

These  figures  are  called  the  constants1  (or  C)  of 
the  solvents.  They  correspond,  therefore,  to  an 
osmotic  pressure  of  22.4  atmospheres.  The  osmotic 
pressure  of  solutions  is  commonly  calculated  from 
the  depression  of  freezing-point. 

The  apparatus  in  which  the  freezing-point  de- 
terminations are  made  is  known  as  Beckmann's. 
This  consists  of  a  large  test-tube,  to  contain  the 
substance,  suspended  in  a  somewhat  larger  test- 
tube,  so  as  to  form  an  air-jacket  between  the  two 
tubes.  The  outer  test-tube  is  placed  in  a  freezing- 
mixture  of  iced  water  and  salt  contained  in  an 
earthenware  jar  (which  has  been  wrapped  round 
with  flannel  to  diminish  the  heat-conduction). 
The  freezing-mixture  is  stirred  with  a  loop  of  wire 
as  represented  in  the  diagram.  In  the  inner  test- 
tube  is  suspended  the  bulb  of  a  Beckmann  ther- 
mometer. This  thermometer  does  not  give  ab- 
solute readings  of  temperature  as  does  an  ordinary 
thermometer.  It  is  used  only  for  demonstrating 
the  difference  in  temperature  at  which  two  solu- 
tions freeze,  or  with  certain  modifications  it  may 

1  The  constants  are  not  always  exactly  those  given  above. 
Some  substances  give  a  depression  of  freezing-point  of  water, 
indicating  a  constant  of  1.84  or  1.85.  The  constant  for  benzol 
seems  to  vary  from  4.85  to  5.15. 


MOLECULAR  WEIGHT  DETERMINATION 


61 


be  used  to  tell  the  different  temperatures  at  which 
two  solutions  boil.  Before  the  thermometer  is 
used  for  freezing-point  determinations,  the  menis- 
cus of  the  mercury  column  must  be  adjusted  so  that 
it  stands  within  the  scale -(high  up)  at  the  tempera- 
ture at  which  the  solvent  used 
freezes  or  crystallizes.  To  make 
this  adjustment  the  bulb  of  the 
thermometer  is  placed  in  iced 
water  ^  and  if  it  be  found  that 
there  is  too  much  mercury  to 
bring  the  meniscus  within  the 
scale,  then  the  upper  end  of  the 
thermometer  is  tapped  with  the 
fingers  so  as  to  cause  the  mer- 
cury at  the  top  of  the  reservoir, 
which  is  connected  with  the 
upper  end  of  the  thermometer 
tube,  to  fall  to  the  bottom  and 
so  to  become  disconnected  from 
the  mercury  column  in  the 
thermometer  tube.  Should  the 
meniscus  of  mercury  stand  be- 


low 3.5°  on  the  scale  at  the 


FIG.  17. 


freezing-point  of  water,  or  of 
the  other  solvent  used,  then  the  thermometer  must 
be  inverted,  and,  by  tapping,  more  mercury  can 
be  added  to  that  in  the  tube. 

For  making  the  actual  freezing-point  determina- 
tion the  inner  tube  of  the  apparatus  is  partly  filled 
with  the  solution  under  examination  so  that  the 
latter  comes  a  little  above  the  bulb  of  the  ther- 


62  ORGANIC  CHEMISTRY 

mometer  (see  Fig.  17).  The  tube  is  then  placed 
directly  in  the  freezing-mixture  until  the  mercury, 
having  fallen  to  its  lowest  level,  begins  to  rise 
again,  when  the  tube  is  removed  quickly  from 
the  freezing-mixture  and  placed  in  the  larger  test- 
tube,  as  before  described.  The  cooling  is  then 
proceeded  with  until  the  meniscus  of  mercury 
stands  at  a  constant  level.-  During  cooling,  the 
fluid  is  kept  constantly  in  motion  by  means  of  a 
platinum  wire,  bent  into  a  loop  as  shown  in  the 
diagram.  The  reading  is  taken  whenever  constant 
and  compared  with  the  reading  obtained  when  pure 
water  (or  whatever  other  solvent  is  used)  is  frozen. 
This  difference  is  designated  by  A.1 

Since  this  constancy  of  (7,  for  any  given  solvent, 
is  the  point  on  which  the  method  depends,  the 
following  experiment  should  be  performed  to 
demonstrate  that  for  water  C  has  the  value  given 
to  it  above. 

EXPERIMENT.  Weigh  out  a  quantity  of  pure 
dry  urea  corresponding  to  one-tenth  its  molecular 
weight  in  grams  (i.e.,  6  gm.);  dissolve  this  in  100 

1  Care  should  be  taken  that  the  supercooling  is  not  excessive. 
If  this  be  so,  a  correction  is  necessary  because  the  formation 
of  ice  (pure  water)  lessens  the  volume  of  the  solution,  and  there- 
fore, the  depression  is  greater  than  it  would  be  if  only  a  trace  of 
ice  is  present.  For  aqueous  solutions  1.25%  of  A  is  added  to 
the  observed  thermometer  reading  for  each  degree  centigrade 
of  supercooling,  and  by  deducting  from  the  freezing-point 
of  water  the  true  A  is  obtained.  For  example,  suppose  the 
freezing-point  of  water  was  at  3.9°,  that  of  the  solution  at  2°, 
and  the  point  of  supercooling  at  0°.  A  is  1.9,  then  1.9(2  x  .0125) 
=  .047,  2 +.047  =2.047;  3.9° -2.047  =  1.853=  corrected  A. 


MOLECULAR  WEIGHT  DETERMINATION  63 

gm.  of  distilled  water.  Compare  the  freezing- 
point  of  this  solution,  corrected  for  supercooling, 
with  that  of  pure  water.  Does  it  correspond  to 
the  constant?  Also  calculate  the  molecular  weight 
of  urea. 

In  determining  the  molecular  weight  of  any 
substance  we  must  first  of  all  choose  the  most 
suitable  solvent  for  it,  and,  in  an  accurately 
weighed  quantity  of  this  dissolve  an  accurately 
weighed  quantity  of  the  substance  under  examina- 
tion. Knowing  what  C  for  our  solvent  is, — in 
other  words,  through  how  many  degrees  centi- 
grade the  freezing-point  of  our  solution  would  be 
lowered  were  a  gram-molecular  quantity  per 
1000  gm.  of  solvent  taken, — if  we  find  the  freezing- 
point  actually  lowered  to  a  less  extent  than  this, 
we  know  that  less  than  a  gram-molecule  must  have 
been  dissolved,  the  actual  amount  less  than 
this  being  proportional  to  the  difference  from 
C  recorded  by  the  thermometer.  In  other 
words,  the  depression  observed,  represented 
by  A,  is  to  C  as  the  strength  of  the  solution 

.   /weight  of  substanceX  .  - 

used  I  -  -  )  is  to  that  of  a  gram- 

\   weight  of  solvent   / 

molecular  solution  (or  rather  a  solution  containing 
a  gram-molecule  dissolved  in  1000  gm.  of  solvent). 

S>     C1 
m=—X—,  where  S  equals  the  weight    of   sub- 

L     A 

stance  used  in  grams;   L,  the  weight  of  solvent  in 

S 
grams.     — ,  when  solved,  gives  a  decimal  fraction 


64  ORGANIC  CHEMISTRY 

expressing  what  part  of  1  gm.  of  the  substance  is 
dissolved  in  1  gm.  of  solvent;  therefore,  to  cal- 
culate the  gram-molecule  (the  amount  dissolved 
in  1000  gm.  of  solvent),  ra  must  be  multiplied  by 
1000,  and  M  equals  the  molecular  weight  in  the 

S     C 

equation  M -—  X—  XlOOO.      For  example,  the   A 
L    A 

of  a  1%  cane-sugar  solution  is  about  0.054°. 
The  molecular  weight  of  the  sugar,  therefore,  is 

1  1    QA 

X— — XlOOO  =344.     According  to  the  formula 

Ci2H22Oii,  it  should  be  342. 

The  A  of  blood  and  of  urine  are  sometimes  determined.  That 
of  human  blood  is  about  0.55°.  In  case  of  drowning  the  blood 
is  diluted,  therefore  the  A  is  much  less;  if  a  person  were  killed 
before  being  thrown  into  the  water,  the  A  would  not  be  lessened. 

IONIZATION 

The  method  is  not,  however,  applicable  to  all 
substances,  even  though  they  be  readily  soluble 
in  the  above-mentioned  solvents.  Weight  normal 
solutions  of  certain  substances  give  a  depression 
of  freezing-point  greater  than  C.  Practically  all 
metallic  salts  and  most  acids  and  bases  when  in 
aqueous  solution  are  included  in  this  category. 
To  demonstrate  this  let  us  determine  the  depres- 
sion of  freezing-point  produced  by  a  gram-molecular 
solution  of  sodium  chloride. 

EXPERIMENT.  Weigh  out  one-tenth  (one- 
twentieth  is  better)  the  molecular  weight  of  pure 
sodium  chloride  in  grams  and  dissolve,  as  in  the 


IONIZATION  65 

case  of  urea,  in  100  c.c.  of  pure  distilled  water. 
Determine  the  depression  of  the  freezing-point 
in  Beckmann's  apparatus.  It  will  be  found  to  be 
considerably  greater  than  1.86  (viz.,  about  3.35). 

Knowing  that  1.86  is  A  for  a  gram-molecular 
solution,  it  is  easy  to  calculate  how  many  gram- 
molecules  per  liter  (X)  a  A  of  3.35  will  represent, 
thus: 

1.86  :  1::3.35  :  X]  X  =  1.8. 

To  ascertain  the  actual  osmotic  pressure  of  the 
sodium  chloride  solution  we  must  accordingly 
multiply  22.4  atmospheres  by  1.8.  This  gives 
us  about  40  atmospheres. 

What  then  is  the  cause  of  this  deviation  from  the 
law?  The  answer  to  the  question  is  furnished  by 
comparing  the  electrical  conductivities  of  the  two 
classes  of  solutions.  Solutions  of  those  substances 
which  obey  the  above  law  will  be  found  to  be  bad 
conductors  of  electricity — non-electrolytes — whereas 
solutions  of  those  substances  which  do  not  obey  it 
will  be  found  to  be  good  conductors — electrolytes. 
This  discovery,  viz.,  that  solutions  which  con- 
duct electricity  appear,  from  the  determination 
of  A,  to  have  a  greater  number  of  molecules  than 
those  which  do  not  conduct,  has  led  chemists  to 
the  conclusion  that  certain  of  the  molecules  in 
such  solutions  must  split  up  into  smaller  parts, 
called  ions,  and  that  it  is  only  when  this  dissocia- 
tion of  molecules  into  ions  takes  place  that  it  is 
possible  for  the  solution  to  conduct  electricity. 


66  ORGANIC  CHEMISTRY 

In  fact,  our  whole  conception  of  the  conduction 
of  electricity  in  solutions  is  based  on  this  hypothe- 
sis. It  is  supposed  that  every  molecule  of  substance 
is  charged  with  positive  and  negative  electricity, 
which  in  the  intact  molecules  so  neutralize  each 
other  that  we  do  not  appreciate  either.  When 
these  molecules  are  suspended  in  solution,  how- 
ever, they  show  a  greater  or  less  tendency  to  split 
up  into  ions,  one  set  of  which  carries  positive  elec- 
tricity and  the  other  negative  electricity.  These 
ions  wander  about  the  solution  much  as  if  they 
were  independent  molecules.  Each  ion  has  as 
much  effect  as  a  molecule  on  the  vapor  pressure, 
osmotic  pressure  and  depression  of  freezing-point 
of  a  solution. 

When  an  electrical  current  is  passed  through  a 
solution  that  has  undergone  dissociation  into  ions, 
the  ions  tend  to  collect  at  the  two  poles  and 
yield  up  their  electrical  charges.  Those  which 
collect  around  the  positive  element  or  anode  are. 
called  anions,  and  those  collecting  around  the 
negative  element  or  cathode  are  called  cations. 
Anions  are  charged  with  negative  electricity,  and 
cations  with  positive  electricity.  Examples  of 
anions  are  OH  and  the  acid  portion  of  salts,  for 
example  864,  Cl,  etc.;  the  cations  include  hydro- 
gen and  metals.  The  ionization  is  not  dependent 
on  the  passage  of  an  electrical  current. 

EXPERIMENT.  Put  some  strong  NaCl  solution 
in  a  beaker,  add  a  few  drops  of  phenolphthalein 
solution,  and  immerse  in  the  liquid  a  pair  of  battery 


ION  I Z  AT  ION  67 

plates,  consisting  of  a  strip  of  sheet  zinc  and  one  of 
copper  soldered  together  at  one  end  and  separated 
in  the  liquid.  As  the  electric  current  passes, 
sodium  ions  travel  to  the  copper  plate  and  give  up 
their  electric  charges,  becoming  metallic  sodium, 
which  attacks  the  water  and  forms  NaOH  in  the 
region  of  the  copper  plate,  therefore  a  pink  zone 
(OH  ions)  appears  at  this  point. 

When  solutions  of  acids  undergo  ionization,  the 
cation  H  is  that  which  confers  the  acidic  properties 
on  the  solution.  An  un-ionized  acid  does  not  act 
like  an  acid;  for  example,  EbSCU  dissolved  in  toluene 
does  not  ionize  and  will  not  give  off  hydrogen  in  the 
presence  of  zinc.  (Also  see  experiment  under  Picric 
Acid,  p.  342).  On  the  other  hand,  hydrogen  itself, 
as  the  gas  or  in  solution,  shows  no  acid  properties. 
We  must  assume,  therefore,  that  the  hydrogen  ion 
is  something  different  from  the  hydrogen  atom. 
The  same  is  true  for  other  ions:  they  are  not  the 
same  as  the  free  elements  or  groups  of  elements; 
they  are  particles  with  opposite  electrical  charges 
which  behave  like  molecules.  It  is  believed  that 
the  ions  are  hydrated,  i.e.,  that  they  hold  molecules 
of  water  intimately  attached  to  them. 

It  is  usual  to  designate  the  various  ions  by  their 
symbols,  affixed  to  which  is  the  sign  *  for  cations 
(e.g.,  H',  Na",  etc.)  and  '  for  anions  (e.g.,  Cl',  NO'a 
etc.).  Some  ions,  however,  must  carry  two  or 
more  units  of  electrical  charge,  for  otherwise  in  the 
case  of  such  a  substance  as  H2S04  there  would  be 
an  excess  of  positive  electricity  in  the  molecule. 


68  ORGANIC  CHEMISTRY 

The  ion  S(>4  must  therefore  carry  two  charges  of 
negative  electricity  and  be  represented  by  the 
sign  SOr/4.  The  valence  of  the  ion  usually  agrees 
with  the  number  of  unit  charges  of  electricity  that 
it  carries. 

The  coefficient  of  dissociation  therefore  indicates 
what  proportion  of  the  molecules  have  become  split 
up  into  ions.  For  molecules  that  can  yield  only 
two  ions  it  cannot  be  greater  than  2,  but  for  those 
splitting  into  more  than  two  ions  it  may  exceed 
this  number.  In  the  concentration  of  a  1%  solu- 
tion KC1  has  a  coefficient  of  1.82,  KN03  1.67, 
K2S04  2.11,  Na2C03  2.18  and  NaCl  1.9. 

The  amount  of  dissociation  that  a  salt  or  acid 
undergoes  in  solution  depends  very  largely  upon 
the  dilution:  the  greater  the  dilution,  the  greater 
the  dissociation.1 

EXPERIMENT.  To  1  c.c.  of  a  saturated  solution  of 
cupric  bromide  add  water  gradually  5  drops  at  a 
time,  and  note  the  color  changes.  When  the  color 
is  a  pure  blue,  determine  whether  it  is  exactly  the 
same  color  as  that  obtained  by  diluting  solutions 
of  cupric  sulphate,  nitrate  and  acetate.  What  is 
the  blue  color  due  to? 

In  a  solution  of  an  electrolyte  there  is  a  condition 
of  equilibrium  between  molecules  and  ions.  The 
molecules  are  continually  dissociating,  and  simul- 
taneously ions  are  uniting  to  form  molecules.  Re- 

1  For  example,  —  HC1  is  completely  dissociated. 


IONIZATION  69 

actions  between  electrolytes  proceed  rapidly,  be- 
cause as  fast  as  ions  are  used  up  more  molecules 
ionize  in  the  effort  to  restore  equilibrium.  Even  the 
trace  of  H  and  OH  ions  present  in  pure  water  (H  ions 
amounting  only  to  0.0000001  gm.  H  per  L  at  22°) 
facilitates  chemical  reactions.  Most  organic  com- 
pounds react  slowly  because  of  absence  of  ions. 

EXPERIMENT.     To  two  test-tubes  add  a  few  c.c. 
AgNOs  ;  to  one  add  NaBr,  and  to  the  other 


Occasionally,  when  a  substance  is  dissolved,  in- 
stead of  dissociation  there  occurs  a  fusion  or  associ- 
ation of  several  of  the  molecules.  In  such  a  case 
the  freezing-point  or  boiling-point  method  would 
give  too  high  a  molecular  weight.  This  tendency 
to  form  complex  molecules  most  frequently  mani- 
fests itself  when  the  organic  substances  contain 
hydroxyl  or  cyanogen  groups,  and  when  chloroform 
or  benzol  is  used  as  the  solvent.  For  example, 
an  8%  solution  of  phenol  in  benzol  gives  a  depression 
of  freezing-point  indicating  a  molecular  weight  of 
188,  which  is  twice  that  called  for  by  the  formula, 
C6H5OH. 

Many  liquids  polymerize,  that  is,  their  molecules 
associate.  The  condition  of  water  is  supposed  to  be 
represented  by  (H2O)4.2  Liquid  hydrocyanic  acid 
is  (HCN)e.  Next  in  order  of  association  are  formic 
acid  and  methyl  alcohol.  The  greater  the  polym- 

2H20,  (H20)2,  and  (H20)3  are  also  present.  Some  chemists 
think  that  liquid  water  is  a  mixture  of  these  three  (but  mainly 
dihydrol),  and  that  ice  is  trihydrol,  while  steam  is  monohydrol, 


70  ORGANIC  CHEMISTRY 

erization  of  the  solvent,  the  greater    will  be    the 
dissociation  of  an  electrolyte. 

EXPERIMENT.  Add  a  few  drops  of  phenol- 
phthalein  solution  to  25  c.c.  of  neutral  ethyl  alcohol, 
then  one  drop  of  concentrated  NH4OH;  there  is  no 
color  change.  Dilute  with  water,  and  a  pink  color 
develops  because  ionization  of  the  hydroxide  takes 
place  in  the  dilute  alcohol. 

HYDROLYTIC  DISSOCIATION 

Many  salts  when  dissolved  in  water,  undergo 
not  only  electrolytic  dissociation,  but  also  hydrolytic 
dissociation.  The  latter  is  induced  by  the  action 
of  water.  Three  classes  of  salts  are  hydrolyzed: 

1.  Salts  formed  by  the  combination  of  a  weak 
base  with  a  strong  acid.     The  hydrolysis  is  illustrated 
in  the  following  equation: 

FeCl3  +HOH  =  FeCl2OH  +  (H  +  Cl) . 

2.  Salts  formed  from  a  strong  base  and  a  weak 
acid: 

KCN+HOH  =  (K+OH)+HCN. 

3.  Salts  formed  from  a  weak  base  and  a  weak 
acid : 

CH3COONH4  +HOH  =  NEUOH  +CH3COOH, 

The  condition  of  the  solutions  is  not  fully  repre- 
sented by  the  above  equations,  because  only  a  cer- 
tain fraction  of  the  solute  is  hydrolyzed  in  each 


SURFACE  TENSION  71 

case.  In  a  one-thirtieth  gram-molecular  solution 
of  aniline  hydrochloride  about  2.6%  of  the  molecules 
are  hydrolyzed  to  aniline  and  hydrochloric  acid. 

A  solution  of  a  salt  of  class  1  is  acid  in  reaction 
because  of  the  ionization'of  the  strong  acid  set  free 
(while  the  basic  product  of  hydrolysis  furnishes  but 
few  OH  ions).  A  solution  of  a  salt  of  class  2  is 
alkaline  because  the  strong  base  liberated  yields 
so  many  OH  ions,  but  the  weak  acid  hardly  ionizes 
at  all.  A  solution  of  a  salt  of  class  3  will  be  neutral 
if  both  base  and  acid  are  equally  weak,  because  the 
effect  of  the  few  H  ions  from  the  acid  is  neutralized 
by  that  of  the  correspondingly  few  OH  ions  from  the 
base. 

EXPERIMENT.  Dissolve  a  little  potassium  citrate 
in  1  c.c.  of  distilled  water.  In  similar  manner  pre- 
pare a  solution  of  phenylhydrazine  hydrochloride. 
Test  each  with  litmus  paper. 

SURFACE   TENSION 

The  molecules  of  a  liquid  are  attracted  to  one  an- 
other in  all  directions,  these  attractions  neutraliz- 
ing one  another.  At  the  surface,  however,  the 
molecules  are  attracted  by  the  molecules  below  and 
at  the  sides,  but  as  there  is  no  counterbalancing 
attraction  above  there  results  a  definite  pressure 
called  surface  tension.  The  pressure  crowds  the 
molecules  closer  together.  Surface  tension  is  equiv- 
alent, then,  to  the  stretching  of  an  elastic  mem- 
brane at  the  surface.  Fine  powders  of  such  a  nature 
that  they  do  not  readily  take  up  moisture  (as 


72  ORGANIC  CHEMISTRY 

sulphur)  float  when  sprinkled  on  water;  the  par- 
ticles rest  on  the  surface  exactly  the  same  as  if  on  a 
membrane.  If  the  surface  tension  is  lowered,  as 
results  when  bile  salts  are  dissolved  in  the  water, 
such  particles  will  not  be  buoyed  up,  but  will 
sink.  Surface  tension  is  manifested  also  wherever 
the  liquid  comes  in  contact  with  the  supporting 
vessel. 

The  effect  of  surface  tension  is  very  noticeable 
in  the  case  of  small  amounts  of  liquid  under  cer- 
tain circumstances.  If  a  little  water  is  dropped 
on  an  oily  or  paraffined  surface,  it  will  not  spread 
out  in  a  film,  but  will  gather  together  into  drops. 
The  small  drops  are  almost  spherical,  while  the  large 
drops  are  flattened.  Surface  tension  causes  the 
liquid  to  assume  the  form  that  has  the  least  surface, 
that  is,  the  spherical.  Unless  the  drop  is  very 
small,  the  pull  of  gravity  will  modify  the  effect 
of  surface  tension.  When  a  drop  forms  at  the  tip 
of  a  pipette,  it  appears  to  be  exactly  spherical  while 
small,  but  as  it  grows  in  size  it  assumes  a  some- 
what bag-like  shape.  The  drop  falls  when  its 
weight  becomes  great  enough  to  overcome  the 
tension  which  has  been  holding  it  suspended. 
The  surface  tension  of  a  liquid  may  be  determined 
by  finding  the  weight  of  the  drops  delivered  from  a 
stalagmometer.  For  accurate  estimations  the  tip 
of  the  instrument  must  be  of  a  certain  diameter 
and  must  have  been  standardized;  also  the  drops 
must  form  slowly  and  have  a  typical  shape.  A 
correction  must  be  made  for  temperature.  Or- 
dinarily it  suffices  to  count  the  number  of  drops 


SURFACE  TENSION  73 

produced  by  emptying  a  stalagmometer,  and  to 
compare  with  the  number  of  drops  of  water  delivered 
from  the  instrument  at  the  same  temperature. 
Allowance  must  be  made  for  the  density  of  the 
liquid.  The  formula  for  the  calculation  of  the  sur- 
face tension  as  dynes  is  as  follows:  Dynes  per 

Number  of  drops  of  water 

cm.=— T-r-     -TT: — —  X  specific  gravity 

Number  of  drops  of  liquid 

X73. 

The  factor  73  is  the  surface  tension  of  pure  water 
in  dynes,  determined  for  a  line  at  the  surface  of  the 
water  one  centimeter  in  length. 

Capillarity  is  due  to  surface  tension.  If  a  glass 
plate  is  suspended  in  water,  the  liquid  will  wet 
the  glass  for  some  distance  above  the  surface  of 
the  water.  This  amounts  to  an  increase  in  the 
total  surface.  But  the  force  of  surface  tension 
combats  an  increase  in  surface,  and  tends  to  pull 
the  surface  into  the  least  possible  area.  This  it 
does  by  raising  water  at  the  junction  of  the  surface 
with  the  glass,  so  that  the  surface  curves  upward  on 
to  the  glass.  The  area  of  the  surface  along  this 
curved  portion  is  much  less  than  the  area  of  the 
surface  in  this  region  if  it  could  lay  flat  plus  the 
area  of  the  vertical  film  of  water  on  the  glass  plate. 
The  weight  of  water  raised  is  dependent  on  the 
length  of  contact  of  the  water  with  the  glass. 
The  curved  portion  of  the  surface  is  called  the 
meniscus. 

If  a  number  of  glass  tubes  of  different  internal 
diameters  are  placed  in  water,  the  effect  of  capil- 
larity seems  to  be  different  in  the  various  tubes. 


74  ORGANIC  CHEMISTRY 

In  a  wide  tube  there  is  only  the  formation  of  a 
meniscus;  this  is  exactly  the  same  effect  as  with  the 
glass  plate,  the  only  difference  being  in  the  curve 
of  the  glass  wall.  In  a  narrower  tube  the  water  is 
raised  slightly,  because  the  amount  of  water  en- 
closed in  the  tube  is  greatly  diminished  in  propor- 
tion to  the  number  of  vertical  lines  of  contact,  and 
there  will  not  be  a  sufficient  weight  of  water  in  a 
meniscus  to  balance  the  pull,  therefore,  a  column 
of  water  must  be  raised  to  get  the  requisite  weight. 
In  the  case  of  a  tube  having  a  capillary  bore  the 
amount  of  water  available  for  the  action  of  each 
line  of  contact  is  extremely  small,  and  in  con- 
sequence the  water  is  raised  to  a  considerable  height. 
The  relative  surface  tension  of  a  liquid  may  be 
determined  by  measuring  the  height  of  the  column 
of  liquid  in  a  capillary  tube,  and  comparing  with  the 
height  of  the  column  of  water  when  the  same  tube 
is  used  in  water.  The  reading  must  be  corrected 
for  the  specific  gravity  of  the  liquid,  so  that  the 
comparison  made  will  be  of  weights  of  liquids  raised. 
The  absolute  surface  tension  can  be  calculated,  if 
the  diameter  of  the  capillary  is  known.  Many 
organic  liquids,  such  as  methyl  and  ethyl  alcohols, 
ether,  chloroform,  glycerol,  acetone,  aniline,  pyri- 
dine,  phenol  and  certain  organic  acids,  have  a  low 
surface  tension;  on  the  other  hand  when  they  are 
dissolved  in  water  they  lower  the  surface  tension  of 

the  water. 

•  -~* 

EXPERIMENTS.     (1)  Fill  a  test-tube  with  water, 
and  another  with  0.1%  solution  of  castile  soap;  on 


SURFACE  TENSION  75 

the  surface  of  each  liquid  dust  a  few  very  fine  par- 
ticles of  sulphur.  The  sulphur  sinks  in  the  soap 
solution.  Dilutions  of  the  soap  may  be  made  to 
find  how  dilute  a  solution  still  shows  marked  lower- 
ing of  surface  tension.  • 

2.  Place  a  little  paraffin  on  a  small  glass  plate, 
and  melt  it  by  warming  over  a  flame,  so  that  a 
smooth  layer  is  obtained.     Attempt  to  spread  water 
as  a  film  over  the  paraffin.     Observe  the  shape  of 
small  and  of  large  drops  of  water  that  stand  on  the 
paraffin. 

3.  Pour  about  10  c.c.  of  saturated  K2COs  into  a 
test-tube,    and   add   a   few   drops   of   chloroform. 
Notice  that  the  latter  forms  a  layer  on  the  car- 
bonate.    Hold  the  test-tube  obliquely,   and  pour 
down  the  wall  about  5  c.c.  of  water,  but  do   not 
mix  the  liquids.     Why  does  the  chloroform  refuse 
to  remain  as   a  layer  between  the  two   aqueous 
liquids? 

4.  Count    the    drops    delivered    from    a    stalag- 
mometer,    using    (in  the   order  indicated)    ether, 
chloroform,    alcohol    and    water.     Use    suction    to 
dry  the  tube  before  each  filling.     A   1   or  2  c.c 
pipette  having  a  fine  tip  may  be  substituted  for  the 
stalagmometer,   if  necessary.     In  order  to  secure 
slow  dropping,  attach  a  piece  of  rubber  tubing,  and 
use  a  pinchcock  to  control  the  outflow.     Do  not 
handle  the  glass  parts  after  filling;    and  keep  the 
apparatus  in  a  vertical  position  (since  the  size  of 
the  drops  may  be  different  if  held  in  an  inclined 
position).     Calculate  the  surface  tension  of  each 
liquid  by  means  of  the  formula  given  above. 


76  ORGANIC  CHEMISTRY 

5.  Compare  the  relative  surface  tensions  of  ether, 
chloroform,  alcohol,  and  water,  after  having  meas- 
ured the  height  of  the  column  of  liquid  raised  in 
a  graduated  capillary  tube  of  medium-sized  bore. 
After  using  the  tube  in  one  liquid  dry  it  by  suction 
before  placing  it  in  another.  Before  comparing  the 
results  multiply  each  reading  by  the  specific  gravity 
of  the  liquid. 

The  surface  of  the  liquid  is  that  part  in  contact 
with  the  air;  this  may  be  called  the  air-liquid  inter- 
face. As  a  matter  of  fact  there  are  other  surfaces. 
For  instance,  wherever  the  liquid  comes  in  contact 
with  the  supporting  vessel  there  is  a  surface,  a 
solid-liquid  interface.  Also,  if  particles  are  sus- 
pended in  the  liquid,  there  is  a  solid-liquid  interface 
about  each  particle.  A  liquid-liquid  interface  ex- 
ists at  the  plane  of  contact  of  two  immiscible 
liquids.  If  hydrated  particles  of  substance  in 
the  liquid  phase  (emulsoid  colloids,  see  p.  81)  are 
present  in  suspension  in  water,  there  is  a  liquid- 
liquid  interface  about  each  particle. 

Surface  tension  is  not  the  same,  quantitatively, 
at  these  various  interfaces.  It  is  stated  that  the 
surface  tension  at  the  solid-liquid  interface  is 
much  greater  than  that  at  the  air-liquid  interface, 
while  it  is  least  at  a  liquid-liquid  interface.  Sur- 
face tension  effects  are  of  considerable  importance 
in  the  case  of  colloidal  particles. 

Inorganic  salts  raise  the  surface  tension  of  the 
water  in  which  they  are  dissolved,  while  most 
dissolved  substances  lower  it.  At  liquid-liquid 


VISCOSITY  77 

interfaces,  however,  all  substances  (including  salts) 
lower  the  surface  tension  of  the  solvent. 

Gases  are  more  soluble  in  liquids  of  low  surface 
tension,  and  the  degree  of  solubility  is  almost  pro- 
portional (inversely)  to.  the  surface  tension.  For 
example,  the  solubility  at  0°  of  C02  in  1  c.c.  of  water, 
alcohol,  and  ether  is  1.713,  4.33,  and  7.33  c.c. 
respectively,  while  the  surface  tensions  of  these 
liquids  are  73,  22  and  16  dynes. 

VISCOSITY 

The  viscosity  of  a  liquid  depends  upon  its  inter- 
nal friction.  The  friction  is  due  to  the  adhesion  of 
the  molecules  of  the  liquid  to  one  another.  A 
measurement  of  this  friction  may  be  made  by 
observing  the  time  required  for  a  certain  quantity 
of  liquid  to  pass  through  a  capillary  tube  and  com- 
paring with  the  time  required  by  an  equal  volume 
of  water  in  the  same  apparatus.  In  the  calculation 
account  must  be  taken  of  the  specific  gravity  of 
the  liquid,  because  increase  in  the  weight  of  the 
column  of  liquid  increases  the  pressure  and,  there- 
fore, increases  the  rate  of  flow. 

We  may  suppose  that  the  layer  of  liquid  in  con- 
tact with  the  wall  is  not  moving,  that  the  next  layer 
is  moving  slowly,  and  that  each  layer  moves  faster 
the  nearer  it  is  to  the  center  of  the  tube.  The  rate 
of  flow  of  the  liquid  as  a  whole  will  depend  upon  the 
amount  of  friction  between  these  successive  layers, 
hence  measurement  of  this  rate  gives  a  basis  for 
calculating  viscosity.  When  liquid  particles  push 
past  one  another  in  this  way,  work  must  be  done, 


78  ORGANIC  CHEMISTRY 

and  the  amount  of  work  necessary  is  dependent 
upon  the  internal  friction. 

Specific  viscosity  is  the  ratio  of  the  viscosity  of  a 
liquid  to  that  of  another  liquid  that  has  been  chosen 
as  a  standard.  For  example,  compared  with  water 
as  unity,  the  specific  viscosity  (at  25°)  of  5%  ethyl 
alcohol  is  1.161,  and  of  5%  ethyl  acetate  is  1.044. 

It  will  not  be  necessary  to  discuss  the  determina- 
tion of  the  absolute  viscosity  of  a  liquid. 

The  temperature  of  the  liquid  must  be  controlled 
when  its  viscosity  is  determined,  since  increase  in 
temperature  diminishes  viscosity.  The  tempera- 
ture should  always  be  reported.  The  coefficients 
for  change  in  viscosity  for  temperature  are  different 
for  different  liquids. 

The  viscosity  of  organic  liquids  belonging  to  an 
homologous  series  (see  p.  104)  increases  in  pro- 
portion to  the  increase  in  molecular  weight. 

The  viscosity  of  the  blood  is  of  great  physiological 
importance.  Fluidity  is  the  reciprocal  of  viscosity. 
In  proportion  as  the  viscosity  is  lessened,  the 
fluidity  is  increased. 

EXPERIMENTS.  (1)  Compare  the  viscosity  of 
water,  and  of  absolute  alcohol  in  an  Ostwald  vis- 
cosity pipette.  To  do  this  pour  about  5  c.c.  of  the 
liquid  into  the  large  tube  and  by  suction  from  a 
suction-pump  draw  it  into  the  small  tube  and 
bulb,  filling  above  the  upper  mark;  disconnect  and 
prevent  the  liquid  flowing  back  by  sealing  the  end 
with  the  finger  (as  in  using  a  pipette);  draw  off 
the  excess  of  liquid  in  the  large  tube  with  a  pipette. 


COLLOIDS  79 

Now  releasing  the  finger  start  a  stop-watch  at  the 
instant  that  the  meniscus  reaches  the  upper  mark 
and  stop  the  watch  when  it  reaches  the  mark  on  the 
capillary  tube. 

2.  Use  a  viscosimetex-  such  as  is  used  for  com- 
mercial chemical  work;  Scott's  is  a  simple  apparatus. 
Try  this  with  water  and  later  with  an  oil  at  the  same 
temperature  (preferably  at  20°).  Each  determina- 
tion is  made  as  follows:  put  200  c.c.  of  the  liquid 
into  the  viscosity  cup,  set  a  graduate  under  the 
cup  to  catch  the  outflow,  press  the  lever  which 
raises  the  plunger  and  at  the  same  instant  start  the 
watch;  when  50  c.c.  has  flowed  out  stop  the  watch 
and  let  the  plunger  fall.  Dividing  the  time  for  the 
oil  by  the  time  for  water  gives  the  figure  for  the 
viscosity  number  1  of  the  oil. 

Now  raise  the  temperature  of  the  oil  20°  and  make 
another  determination. 

COLLOIDS 

Dispersion  of  Substances  in  a  Liquid.  When 
sodium  chloride  dissolves  in  water,  it  forms  what 
we  call  a  true  solution.  The  molecules  of  NaCl, 
and  also  the  Na  and  Cl  ions  are  uniformly  dis- 
tributed throughout  the  mass  of  the  solvent.  In 

In  test'  "le  oil  for 

iter^ti-m  v 
•ocurel  137  acternlnlr 

•     •  •  •     .  ">iuc- 

ed  fro  ail 

The  Ostviald  v 

tic  - 

rfc  of  exnctly 

Gher       ,   0  r     xlc  •         •• 

.  ) 


80  ORGANIC  CHEMISTRY 

the  solution  there  is  both  ionic  and  molecular  dis- 
persion. In  a  true  solution  of  a  substance  that 
does  not  ionize  there  is  only  molecular  dispersion 
of  the  substance. 

On  shaking  an  insoluble  powder  (as  talcum)  with 
water  the  fine  particles  are  scattered  all  through  the 
liquid,  and  seem  to  be  in  uniform  suspension.  This 
condition  is  temporary,  however,  for,  on  standing, 
the  liquid  becomes  clear  and  all  of  the  solid  sub- 
stance is  deposited  at  the  bottom.  In  the  case  of 
some  substances  the  particles  may  be  fine  enough 
to  remain  suspended  for  a  long  time.  Such  a  mix- 
ture is  a  suspension,  not  a  solution. 

Insoluble  liquids  may  be  broken  by  shaking  with 
water  into  minute  droplets.  As  long  as  these 
drops  remain  suspended  the  mixture  is  an  emul- 
sion. In  order  to  form  a  permanent  emulsion  it  is 
generally  necessary  to  use  an  emulsifying  agent. 
This  forms  a  film  about  the  drop,  so  that  it  is  kept 
separate  from  other  drops.  In  cream  the  fat  is 
present  as  a  permanent  emulsion,  the  microscopic 
drops  being  enclosed  by  films. 

Intermediate  between  these  coarse  dispersions 
of  solids  and  liquids  in  liquids,  and  the  molecular 
dispersions  of  true  solutions,  there  is  another  type 
of  dispersion  that  is  characteristic  of  colloidal  solu- 
tions. The  particles  in  a  colloidal  solution  are 
larger  than  the  largest  molecules  in  a  true  solution, 
but  smaller  than  the  smallest  particles  in  a  suspen- 
sion or  emulsion.  The  colloidal  particles  remain 
permanently  suspended.  Some  colloidal  solutions 
are  somewhat  opaque  or  opalescent,  but  others  are 


COLLOIDS  81 

practically  as  clear  as  true  solutions.  One  of  the 
distinguishing  differences  between  colloidal  solu- 
tions and  true  solutions  is  the  fact  that  in  all  colloidal 
solutions  the  particles  have  surfaces  of  contact  with 
the  liquid,  while  in  true-  solutions  there  are  no  sur- 
faces of  contact  of  the  dissolved  substance.  These 
surfaces  are  an  important  factor  in  the  behavior  of 
colloids. 

There  are  two  kinds  of  colloids,  suspensoids  and 
emulsoids.  Suspensoid  particles  are  in  the  solid 
phase,  while  emulsoid  particles  are  in  the  liquid 
phase.  Suspensions  and  suspensoids  are  essentially 
of  the  same  nature,  differing  only  in  the  size  of  the 
particles.  In  appearance,  however,  they  are  dis- 
tinctly different,  since  suspensions  are  invariably 
turbid,  but  suspensoid  solutions  may  be  quite  clear, 
so  that  they  seem  to  be  free  of  solid  particles. 

Emulsions  and  emulsoids  are  not  of  the  same 
nature,  although  both  consist  of  liquid  particles 
suspended  in  liquids.  The  liquid  particles  in  an 
emulsion  are  practically  insoluble,  and  have  no 
affinity  for  the  liquid  in  which  they  are  dispersed. 
Emulsoids,  however,  readily  take  up  the  solvent, 
so  that  the  particles  become  liquid  particles.  The 
solvent  dissolves  in  the  colloidal  substance,  and  the 
latter,  instead  of  becoming  molecularly  dispersed, 
breaks  up  into  infinitely  small  liquid  particles.  In 
the  case  of  colloidal  solutions  in  water  we  may  say 
that  the  emulsoid  particles  are  hydrated. 

Suspensions,  emulsions,  and  colloidal  solutions 
are  heterogeneous  mixtures,  while  true  solutions  are 
homogeneous. 


82  ORGANIC  CHEMISTRY 

In  the  following  classification  of  dispersion  mix- 
tures the  diameter  of  the  particles  is  indicated. 

HOMOGENEOUS   DISPERSIONS 

Ionic  dispersions 

Molecular  dispersions  0 . 1-1 . 0  MM  1 

MICRO-HETEROGENEOUS   DISPERSIONS 

Emulsoids  1.0-100  MM 

Suspensoids  1.0-1 00  MM 

COARSE   HETEROGENEOUS   DISPERSIONS 

Emulsions  greater  than  100  MM 

Suspensions  greater  than  100  MM 

We  must  warn  against  getting  the  idea  that  these 
forms  of  dispersion  are  rigidly  separated  from  one 
another.  It  is  believed  that  all  substances  can  be 
brought  into  colloidal  solution  under  proper  con- 
ditions. Therefore,  it  is  better  to  throw  the  em- 
phasis on  the  colloidal  state,  and  to  avoid  looking 
upon  certain  particular  substances  as  distinctively 
colloidal.  A  true  solution  may  spontaneously  change 
to  a  colloidal  solution.  Thus,  silicic  acid,  when  first 
prepared,  is  in  true  solution,  and  on  standing  be- 
comes mainly  colloidal,  finally  changing  to  a  typical 
colloidal  gel  (see  p.  84).  In  some  cases  there  may 
be  a  trace  of  substance  in  true  solution,  in  equili- 
brium with  that  portion  which  is  in  colloidal  solu- 
tion. It  is  supposed  that,  if  a  substance  has 
extremely  large  molecules,  a  molecularly  dispersed 
1 A  MM  is  one-millionth  part  of  a  millimeter. 


COLLOIDS  83 

solution  of  it  may  have  the  properties  of  a  colloidal 
solution.  For  instance,  haemoglobin  is  considered 
by  some  to  have  single  molecules  as  the  ultimate 
particles  in  solution,  yet  it  is  colloidal.  As  a  rule, 
however,  the  very  smallest  particles  in  a  suspensoid 
or  emulsoid  solution  are  clusters  or  aggregations  of 
many  molecules. 

Behavior  of  Colloidal  Solutions.  Solutions  of  sus- 
pensoids  do  not  gelatinize,  are  not  viscid,  and 
are  coagulated  by  a  small  quantity  of  electrolytes. 
They  are  irreversible  colloids,  that  is,  after  being 
evaporated  the  residue  cannot  be  put  into  colloidal 
solution  again.  The  surface  tension  of  these  solu- 
tions is  practically  the  same  as  that  of  the  pure 
solvent. 

EXPERIMENT.  Prepare  colloidal  Prussian  blue 
as  follows:  measure  into  one  test-tube  10  c.c. 
N/50  ferric  chloride,  into  another  10  c.c.  N/50 
potassium  ferrocyanide,  and  pour  the  two  solutions 
simultaneously  at  the  same  rate  into  a  clean  beaker. 
A  blue  solution  free  of  precipitate  is  secured.  Shake 
some  of  the  solution  in  a  test-tube;  it  does  not  form 
a  foam,  there  is  no  evidence  of  viscidity.  Dilute 
about  5  c.c.  with  25  c.c.  of  distilled  water;  there 
is  no  precipitate.  To  5  c.c.  of  the  diluted  solution 
add  5  c.c.  of  magnesium  chloride  solution.  On 
standing  a  blue  precipitate  forms.  Save  the  more 
concentrated  Prussian  blue  solution  for  a  later 
experiment.  To  test  reversibility  evaporate  5  c.c. 
in  an  evaporating  dish  on  the  water-bath,  and 
attempt  to  redissolve  the  residue. 


84  ORGANIC  CHEMISTRY 

Illustrations  of  suspensions  are:  colloidal  gold, 
colloidal  hydroxides  of  metals  (as  Fe(OH)3),  and 
colloidal  sulphides  of  metals  (as  As2S3). 

Emulsoid  solutions  are  viscid,  they  tend  to  gelatin- 
ize, and  they  are  not  coagulated  by  small  amounts 
of  electrolytes.  After  evaporation  the  residue  can 
be  redissolved,  so  that  they  are  reversible.  They 
are  also  reversibly  soluble  after  precipitation  by 
alcohol  or  certain  salts.  Emulsoid  solutions  usually 
have  a  lower  surface  tension  than  the  pure  solvent. 

EXPERIMENT.  Pour  about  5  c.c.  of  warm  5% 
gelatin  solution  into  a  test-tube.  Shake  well,  the 
frothing  indicates  viscidity.  Cool  the  tube  with 
running  tap  water;  the  solution  becomes  a  jelly. 
Warm  the  tube  until  the  gelatin  liquefies;  pour 
part  of  it  into  an  evaporating  dish  and  evaporate 
to  dryness  on  a  water-bath;  to  the  rest  add  an  equal 
volume  of  magnesium  chloride  solution.  Dissolve 
the  residue  in  the  evaporating  dish  with  hot  water. 
To  a  few  c.c.  of  dilute  gelatin  solution  add  ammonium 
sulphate  crystals,  and  shake.  Filter  off  the  pre- 
cipitated gelatin,  and  dissolve  it  in  hot  water. 

Illustrations  of  emulsoids  are:  silicic  acid,  tannin, 
soaps,  many  of  the  dyes,  gelatin,  albumin  and 
other  proteins. 

A  colloidal  solution  when  in  the  liquid  condition 
is  called  a  sol,  and  when  in  the  gelatinized  state  a 
gel.  If  the  solvent  is  water  the  terms  hydrosol  and 
hydrogel  may  be  used.  When  a  solution  "  gelates," 
a  structure  or  framework  develops  in  the  liquid. 
In  some  cases  the  structure  is  sponge-like,  liquid 


COLLOIDS  85 

being  interspersed  throughout.  In  other  cases 
(e.g.,  13%  gelatin)  the  liquid  is  held  as  separate 
droplets  imprisoned  in  the  solid  gel  substance. 

Diffusion  of  Colloids.  The  rate  of  diffusion  of 
typical  colloids  is  only  one-hundredth  of  that 
of  the  most  rapidly  diffusing  electrolytes,  and  about 
one-tenth  of  that  of  cane  sugar.  Diffusion  may  be 
tested  by  bringing  the  solution  and  solvent  to- 
gether, but  separated  by  an  easily  permeable 
membrane.  Crystalloids  diffuse  into  soft  colloidal 
gels,  passing  along  the  liquid  pathways  of  the  gel 
almost  as  readily  as  they  diffuse  in  a  liquid.  Col- 
loids, however,  diffuse  very  slowly  into  gels. 

EXPERIMENT.  Take  two  test-tubes  containing 
1%  agar-agar  solution  in  the  gel  state.  Into  one 
pour  Prussian  blue  solution;  into  the  other  pour 
some  ammoniacal  copper  hydroxide  solution  (to 
5  c.c.  concentrated  copper  sulphate  solution  add 
ammonia  water  until  the  precipitate  is  just  redis- 
solved).  Let  the  tubes  stand  an  hour  or  more; 
the  Cu  solution  penetrates  the  agar,  while  the  col- 
loidal suspension  does  not.  At  the  end  of  the 
session  empty  the  tubes,  leaving  the  agar  in,  rinse 
out;  and  note  the  condition  of  the  agar.  In  which 
tube  is  agar  colored  blue? 

Dialysis.  Colloids  will  not  diffuse  through  a 
gelatinous  partition  such  as  an  animal  membrane 
or  parchment  paper,  but  crystalloids  pass  through  it 
quickly.  Certain  colloids  are  said  to  dialyze  to  a 
slight  extent.  It  may  be  that  in  these  cases  there 
is  a  trace  of  the  substance  in  true  solution  main- 


86  ORGANIC  CHEMISTRY 

tained  in  equilibrium  with  the  colloidally  dissolved 
substance;  then  it  would  be  expected  that  more  of 
the  colloidal  substance  would  go  into  .true  solution 
as  fast  as  the  molecularly  dispersed  part  passes 
through  the  dialyzer  membrane,  so  that  slow 
continuous  dialysis  would  take  place. 

Ultra-filtration.  By  impregnating  pieces  of  filter- 
paper  with  gelatin  of  different  concentrations  from 
2  to  10%,  and  then  hardening  the  gel  by  exposure 
to  formaldehyde,  filter  disks  can  be  obtained  in 
which  there  is  a  gradation  in  the  size  of  the  pores. 
The  10%  gelatin  produces  a  filter  having  the  small- 
est size  pores;  this  filter  holds  back  almost  all 
colloidal  particles.  Working  with  a  set  of  these 
filters,  results  are  obtained  that  enable  one  to 
arrange  a  list  of  colloidal  solutions  in  the  order  of 
the  size  of  their  particles.  In  the  following  list 
Prussian  blue  has  the  largest,  and  dextrin  the 
smallest  particles 

Prussian  blue. 

Colloidal  ferric  hydroxide  (about  44  /*/*). 

Casein  (in  milk). 

Collargol  (about  20  MM). 

1  per  cent  gelatin. 

1  per  cent  haemoglobin. 

Serum  albumin. 

Albumoses. 

Dextrin. 

As  a  rule  suspensoid  particles  are  much  larger  than 
emulsoid  particles. 


COLLOIDS  87 

Optical  Properties.  A  microscope  of  the  highest 
power  (2250  magnifications)  can  detect  a  body 
140  w  in  diameter.  The  particles  in  most  sus- 
pensions and  emulsions  can,  therefore,  be  seen. 
These  microscopic  particles  have  been  named 
microns.  Visual  evidence  of  the  existence  of  col- 
loidal aggregations  in  a  solution  can  be  obtained 
by  using  the  ultramicroscope.  A  microscope  is 
used,  but  the  illumination  is  from  one  side  instead 
of  from  below.  An  intense  beam  of  light  from 
an  arc  lamp  is  passed  through  a  special  condenser, 
so  that  it  is  focused  to  a  point  within  the  solution 
directly  under  the  lens  of  the  objective.  The 
colloidal  particles  diffract  the  light,  so  that  some 
rays  pass  up  through  the  microscope.  This  diver- 
sion of  light  is  on  the  same  principle  as  the  Tyndall 
phenomenon  observed  in  the  scattering  of  light  by 
dust  particles,  when  a  sunbeam  passes  into  a 
darkened  room.  The  light  is  polarized.  The  par- 
ticles appear  as  dots  or  tiny  specks  of  light  on  a 
dark  background.  Those  that  can  be  seen  as 
separate  points  of  light  are  called  submicrons.  In 
some  solutions  the  particles  are  so  small  that  they 
cannot  be  detected,  but  they  cause  a  haze  of  light 
to  be  seen;  these  are  called  amicrons.  The  particles 
in  colloidal  solutions  of  metals  have  a  greater  power 
to  diffract  light  than  those  in  other  colloidal  solu- 
tions, so  that  particles  of  colloidal  gold  as  small  as 
3-5  nfj.  (about  10  times  the  size  of  alcohol  and  ether 
molecules)  have  been  detected. 

In  the  case  of  emulsoids  the  particles  exert  so 
much  weaker  action  in  diffracting  the  light,  that 


88  ORGANIC  CHEMISTRY 

they  cannot  be  seen  as  submicrons  unless  their 
diameter  is  at  least  30  /*/*.  Most  emulsoid  solu- 
tions show  a  haze  of  light,  and,  therefore,  have 
amicrons.  Submicrons  have  been  observed  in  al- 
bumin, gelatin,  glycogen,  and  agar  hydrosols. 
Diluting  a  solution  may  cause  amicrons  to  take  the 
place  of  submicrons.  Heating  some  solutions  (as 
3%  soluble  starch  or  0.01%  gelatin)  can  change 
submicrons  to  amicrons.  In  the  presence  of  elec- 
trolytes (or,  in  some  cases,  alcohol)  the  particles 
are  aggregated  into  larger  clumps,  and  appear  large 
in  the  ultra-microscope. 

Motion  of  the  Particles.  Colloidal  particles  are 
constantly  in  motion  (Brownian).  Submicrons  have 
been  observed  to  trace  a  zigzag  course.  The  motion 
of  large  particles  is  oscillatory.  The  premanency 
of  suspension  of  the  colloidal  particles  is  largely 
due  to  their  motion.  Increase  in  the  viscosity  of 
a  solution  lessens  Brownian  movement. 

Surface  Tension  of  Colloidal  Solutions.  Suspensions 
and  suspensoid  solutions  have  practically  the  same 
surface  tension  as  the  pure  liquid.  Emulsoids, 
however,  affect  the  surface  tension;  some  increase 
it  (e.g.,  starch  and  gum  arabic),  and  others  lower 
it  (e.g.,  dextrin,  gelatin,  egg  albumin,  tannic  acid, 
fats,  resins  and  soap).  This  difference  in  behavior 
can  be  taken  advantage  of  for  the  purpose  of  dis- 
tinguishing emulsoids  from  suspensoids  Venetian 
soap  (olive  oil  soap)  has  a  marked  effect  in  high 
dilution,  thus  a  0.004%  solution  has  a  very  low  sur- 
face tension.  The  surface  tension  of  emulsoid 
solutions  is  changed  by  H  ions,  OH  ions,  and  by 


COLLOIDS  89 

salts.  Rise  of  temperature  decreases  surface  ten- 
sion. Surface  tension  effects  take  place  within 
all  colloidal  solutions,  since  there  is  a  surface  of  the 
liquid  presented  to  the  surface  of  each  particle  in 
the  solution. 

How  important  this  is  in  a  consideration  of  col- 
loidal solutions  will  be  understood  by  noticing  the 
enormous  increase  of  surface  exposure  when  a  sub- 
stance is  divided  into  fine  particles.  A  compact 
sphere  of  substance  one  mm.  in  diameter  (surface 
area  of  0.0314  sq.  cm.),  if  broken  up  into  particles 
of  uniform  size,  corresponding  to  the  size  of  the  larg- 
est suspensoid  particles  (O.lju),  will  acquire  a  sur- 
face area  of  314  sq.  cm.  If  a  colloidal  solution  is 
purified,  that  is,  freed  of  other  dissolved  substances, 
the  surface  tension  about  the  particles  becomes 
higher,  and  as  it  becomes  higher,  the  difference 
in  potential  increases  and  the  particles  divide  into 
smaller  particles. 

Viscosity  of  Colloidal  Solutions.  Suspensoid  solutions 
have  a  viscosity  but  slightly  different  from  that  of 
the  pure  solvent.  A  3.85%  solution  of  a  colloidal 
silver  compound  was  found  to  be  only  1%  more 
viscid  than  pure  water.  Some  emulsoids  (as  agar- 
agar)  show  great  viscosity  in  low  concentrations. 
Most  emulsoid  solutions,  if  stronger  than  1%,  have 
increased  viscosity. 

Traces  of  acid  or  of  alkali  increase  the  viscosity  of 
some  emulsoids.  There  is  a  point  of  maximum 
viscosity;  for  example,  with  gelatin  solution  the 

N 
maximum  viscosity  with  HC1  is  secured  when 


90  ORGANIC  CHEMISTRY 

is  present.     The  maximum  viscosity  with  NaOH 

N 
is  the  same,  but  is  obtained  when is  present. 

Increase  of  temperature  lessens  the  viscosity. 
But  in  the  case  of  albumin  solutions  a  marked 
increase  in  viscosity  has  been  observed  at  a  temper- 
ature slightly  below  that  at  which  heat  coagulation 
occurs.  ' 

Osmotic  Pressure  of  Colloids.  Osmotic  pressure 
has  been  demonstrated  with  some  colloidal  solu- 
tions. Haemoglobin  in  3%  solution  gave  12  mm. 
mercury  pressure,  and  in  6%  solution  22  mm. 
The  osmotic  pressure  of  1.5%  gelatin  was  found  to 
be  8  mm.,  and  that  of  1.5%  egg  albumin  was  25.6 
mm.  For  these  determinations  a  dialyzing  mem- 
brane was  used  as  the  osmotic  membrane,  so  that 
the  effect  of  impurities  was  neutralized,  since  these 
dialyzed  until  there  was  exactly  the  same  con- 
centration of  them  in  the  liquids  on  both  sides  of 
the  membrane.  Apparently  the  colloidal  particle 
exerts  the  same  effect  in  causing  osmotic  pressure 
as  a  molecule  of  a  crystalloid.  The  number  of 
molecules  aggregated  together  into  a  colloidal 
agglomerate  is  variable  and  may  be  different  at 
different  times  in  the  same  solution.  Whenever 
the  colloidal  clumps  become  larger  the  osmotic 
pressure  is  lessened. 

Molecular  Weight  of  Colloids.  The  true  molecular 
weight  cannot  be  calculated  from  the  osmotic 
pressure,  because  the  number  of  molecules  in  the 
colloidal  particle  can  not  be  determined.  Exactly 
the  same  difficulty  applies  to  molecular  weight  deter- 


COLLOIDS  91 

mination  by  the  freezing-point  method.  The  read- 
ings for  depression  of  freezing-point  are  too  low  to 
be  made  use  of,  since  a  solution  which  has  an  osmotic 
pressure  of  50  mm.  gives  only  0.005°  depression. 
In  the  case  of  haemoglobin  the  smallest  possible 
molecular  weight  can  be  calculated  from  the  con- 
tent of  iron  on  the  supposition  that  each  molecule 
contains  one  atom  of  iron;  but  it  does  not  necessarily 
follow  that  this  minimum  is  the  correct  molecular 
weight. 

Electrical  Charges  of  Colloids.  The  particles  in 
a  colloidal  solution  carry  positive  and  negative 
charges  of  electricity;  and,  since  the  charges  are 
all  of  the  same  kind,  the  particles  repel  one  another. 
This  repulsion  is  a  factor  of  importance  in  main- 
taining the  stability  of  a  colloidal  solution.  When 
a  current  of  electricity  is  passed  through  a  colloidal 
solution,  the  particles  travel  to  one  electrode,  to 
the  cathode  if  they  are  electro-positive,  but  to  the 
anode  if  they  are  electro-negative.  This  process 
is  called  cataphoresis  or  electrophoresis.  The  nature 
of  the  electrical  charge  is  determined  by  this  method. 

Most  suspensoids  are  electro-negative,  but  a 
few  (as  the  hydroxides)  are  electro-positive.  Prac- 
tically all  emulsoids  that  are  of  importance  physio- 
logically are  electro-negative.  Haemoglobin,  how- 
ever, is  electro-positive.  An  albumin  solution,  that 
had  been  purified  so  as  to  free  it  of  electrolytes  to 
the  highest  degree,  showed  no  cataphoresis;  but 
when  acid  was  added  to  the  solution,  the  colloid 
became  electro-positive  (effect  of  H  ions),  and, 
when  alkali  was  added,  it  became  electro-negative 


92  ORGANIC  CHEMISTRY 

(effect  of  OH  ions).  Some  favor  the  view  that  most 
emulsoids  would  be  found  to  be  electrically  neutral, 
if  sufficiently  purified.  In  their  natural  environ- 
ment in  vegetable  and  animal  tissues,  emulsoids 
would  never  be  electrically  neutral.  Many  of  the 
dyes  are  emulsoids,  some  being  electro-positive,  and 
others  electro-negative. 

Precipitation  of  Colloids.  If  two  suspensoids  of 
opposite  electrical  sign  are  mixed  in  such  pro- 
portions that  there  are  just  as  many  positive  as 
negative  charges  present  in  the  mixtures,  maxi- 
mum mutual  precipitation  occurs.  The  oppositely 
electrified  particles  attract  each  other,  and  when 
they  meet  the  charges  are  neutralized.  This  change 
in  electrical  condition  lowers  the  surface  tension 
about  the  particles,  so  that  larger  colloidal  clumps 
must  necessarily  be  formed.  The  agglomeration  of 
the  colloidal  masses  progresses  steadily  until  they  are 
large  enough  to  separate  out  as  a  precipitate.  The 
Brownian  movement  aids  in  bringing  the  masses 
together  after  the  factor  of  electrical  repulsion  has 
been  eliminated.  Emulsoids  of  opposite  electrical 
sign  can  cause  mutual  precipitation.  In  this  case, 
also,  there  must  be  the  proper  relative  proportions 
of  the  two  colloids. 

EXPERIMENT.  To  1  or  2  c.c.  of  colloidal  arsenious 
sulphide  solution  x  add  gradually,  a  drop  at  a  time, 

1  Arsenic  sulphide  may  be  prepared  in  colloidal  solution  by 
pouring  a  boiling  hot  saturated  solution  of  arsenious  acid  into 
an  equal  volume  of  cold  water  that  has  been  saturated  with 
H2S.  Continue  the  passage  of  the  H2S  until  the  mixture  retains 


COLLOIDS  93 

colloidal  ferric  hydroxide  (Merck's  dialyzed  iron 
containing  5%  Fe20s) ;  let  it  stand  a  few  minutes 
after  each  addition.  Finally  a  decided  precipitate 
will  be  obtained.  It  is  difficult  to  regulate  the  pro- 
portions just  right.  Maximum  precipitation  is  se- 
cured when  the  mixture  contains  24  parts  by  weight 
of  As2$3  and  13  parts  of  Fe20s. 

Precipitation  by  Salts.  Suspensoids  are  precipitated 
by  ions  of  opposite  electrical  sign;  electro-positive 
colloids,  as  ferric  hydroxide,  are  precipitated  by 
anions,  as  Cl,  SCU,  while  electro-negative  colloids, 
as  arsenious  sulphide,  are  precipitated  by  cations, 
as  H,  K,  Mg.  The  colloidal  particles  attract  the 
ions  carrying  an  opposite  electrical  charge;  their 
electrical  charges  are  thus  neutralized.  In  conse- 
quence precipitation  occurs  for  the  reason  explained 
above.  The  precipitating  power  is  proportional 
to  the  concentration  of  the  ions.  Thus  a  0.7  gram- 
molecular  solution  of  acetic  acid  and  a  0.0038 
gram-molecular  solution  of  hydrochloric  acid  have 
the  same  concentration  of  H  ions,  and  have  the 
same  degree  of  precipitating  action  on  colloidal 
arsenious  sulphide. 

The  precipitating  ions  are  held  by  the  colloidal 
masses  (adsorption,  see  p.  95)  while  the  other 
ions  remain  in  solution. 

Emulsoids  are  not  precipitated  by  small  quanti- 

the  odor  of  the  gas  after  thorough  shaking.  Nowj*emove  the 
free  H2S  by  passing  hydrogen  through  the  solution.  An  opaque 
yellow  liquid  is  secured.  If  there  is  any  precipitate  remove  this 
with  the  aid  of  a  centrifuge. 


94  ORGANIC  CHEMISTRY 

ties  of  electrolytes;  the  latter,  however,  have  an 
effect  on  the  solution.  When  an  electrolyte  is 
added  to  a  solution,  it  concentrates  at  the  inter- 
faces between  the  colloidal  particles  and  the  solvent, 
just  as  it  does  at  the  air-liquid  interface.  Salts 
lower  surface  tension  at  liquid-liquid  interfaces 
(see  p.  76);  and,  since  the  surface  tension  about 
the  colloidal  particles  is  lessened,  the  particles  must 
come  together  to  form  larger  clumps  so  as  to  restore 
the  balance  in  potential.  If  an  emulsoid  solution, 
that  shows  only  amicrons,  is  treated  with  an  elec- 
trolyte, submicrons  will  be  seen  in  it  with  the 
ultra-microscope.  Addition  of  more  electrolyte  in- 
creases the  size  of  the  particles. 

Precipitation  of  emulsoids  occurs  when  large 
amounts  of  very  soluble  salts  are  added;  this  is 
generally  referred  to  as  a  salting-out  process.  The 
explanation  offered  is  that  such  concentrations  of 
salts  act  to  abstract  water  from  the  hydrated  col- 
loidal particles,  so  that  the  latter  are  reduced  to 
the  solid  phase,  and,  therefore,  become  suspensoid 
particles,  which  are  easily  precipitated. 

In  contact  with  water  most  insoluble  substances  acquire 
negative  charges  of  electricity.  For  example,  the  fibers  of 
filter-paper,  wool,  cotton  and  asbestos  become  electro-negative. 
This  is  true  also  of  the  particles  in  most  suspensions,  very  few 
being  electro-positive  (e.g.,  barium  carbonate).  Suspensions 
of  some  fine  powders,  as  lamp-black  or  kaolin,  are  precipi- 
tated by  electrolytes  in  a  similar  manner  as  suspensoids. 
Acids  can  diminish  the  negative  charge,  completely  neu- 
tralize it,  or  even  import  a  positive  charge;  this  effect  is 
undoubtedly  due  to  adsorption  (see  below)  of  the  positive 
H  ions. 


COLLOIDS  95 

Adsorption.  Colloidal  particles  attract  ions  having 
opposite  electrical  charges,  and  hold  them,  but  not 
by  entering  into  chemical  combination.  This  phys- 
ical union  is  described  as  surface  condensation;  and 
the  process  is  called  adsorption. 

Other  substances  besides  ions  are  adsorbed. 
Emulsoids  adsorb  to  suspensoid  particles,  particu- 
larly if  the  colloids  have  opposite  electrical  charges. 
For  example  if  Fe(OH)3  (electro-positive  suspensoid) 
is  mixed  with  a  faintly  alkaline  solution  of  protein 
(electro-negative  emulsoid),  on  adding  a  salt  both 
iron  and  protein  are  completely  precipitated. 

EXPERIMENT.  To  10  c.c.  of  blood  serum  add  70 
c.c.  of  water,  then  15  c.c.  of  colloidal  ferric  hydroxide 
solution  and  add  powdered  sodium  sulphate,  shak- 
ing after  each  addition,  until  a  gelatinous  precipitate 
forms.  Filter,  and  test  the  filtrate  for  protein 
(biuret  test,  p.  282)  with  NaOH  solution  and  a 
drop  of  dilute  CuSO-t. 

Enzymes  are  supposed  to  be  emulsoids.  The 
substrate  (the  substance  that  is  to  be  acted  on)  con- 
denses on  the  surface  of  the  enzyme  particle,  and 
the  rate  of  enzyme  action  at  any  particular  moment 
is  proportionate  to  the  degree  of  adsorption.  Other 
substances  adsorb  to  enzymes,  so  that  it  is  prac- 
tically impossible  to  separate  enzymes  in  pure 
condition. 

The  humus  of  the  soil  is  an  emulsoid  colloid;  it 
plays  an  important  part  in  holding  soluble  salts  in 
the  soil  by  adsorption. 

Dyes  adsorb  to  the  fibers  of  cloth  (see  p.  407). 


96  ORGANIC  CHEMISTRY 

Crystalloids,  enzymes,  and  colloids  adsorb  to 
insoluble  particles  suspended  in  a  liquid.  The 
high  surface  tension  at  the  liquid-solid  interfaces 
about  the  particles  probably  accounts  for  the  inten- 
sity of  the  adsorption  process.  Finely  powdered 
animal  charcoal  is  one  of  the  most  effective  agents 
for  removal  of  substances  from  solution  by  adsorp- 
tion. It  is  used  extensively  for  decolorizing  liquids. 
The  rate  of  adsorption  is  increased  by  shaking,  also 
by  heating;  but  the  total  amount  adsorbed  is  less 
in  a  hot  than  in  a  cold  liquid.  Adsorption  is  re- 
versible, since  the  adsorbed  substance  may  be 
removed,  at  least  in  part.  For  instance,  lactose 
that  has  adsorbed  to  charcoal  may  be  recovered 
by  treating  the  charcoal  with  acetic  acid,  the  more 
easily  adsorbable  acetic  acid  dislodging  the  lactose 
and  being  adsorbed  in  its  stead. 

In  some  cases  not  all  of  the  substance  is  adsorbed, 
the  mixture  coming  to  an  equilibrium  when  a  cer- 
tain proportion  has  been  adsorbed.  Some  solu- 
tions should  not  be  filtered,  because  the  dissolved 
substance  adsorbs  to  the  paper  too  readily. 

In  some  cases  chemical  reaction  follows  adsorp- 
tion. This  is  undoubtedly  what  takes  place  in  the 
manufacture  of  leather;  tannin  being  first  adsorbed 
to  the  tissue  substance  of  the  hide,  and  later  forming 
insoluble  compounds. 

Protective  Colloids.  When  an  emulsoid  is  added  to 
a  suspensoid  solution,  it  exerts  a  protective  action, 
preventing  or  hindering  the  precipitation  of  the 
suspensoid  by  electrolytes.  This  effect  is  believed 
to  be  due  to  adsorption  of  the  emulsoid  on  the  sus- 


COLLOIDS  97 

pensoid,  so  that  the  latter  acquires  the  .character  of 
an  emulsoid. 

EXPERIMENT,  (a)  To  5  c.c.  of  N/20  silver  nitrate 
solution  add  three  drops  nitric  acid  and  5  c.c.  of 
N/20  sodium  chloride;  a  curdy  precipitate  is  ob- 
tained. 

(6)  Into  one  test-tube  put  5  c.c.  N/20  silver 
nitrate,  3  drops  nitric  acid  and  about  1  c.c.  gelatin. 
Into  another  put  5  c.c.  NaCl  and  1  c.c.  gelatin. 
Empty  both  simultaneously  and  at  the  sanle  rate 
into  a  beaker.  An  opalescent  solution  (milky) 
which  resembles  glycogen  solution  is  obtained. 
Now  dilute  and  note  carefully  absence  of  precipitate. 

Photographic  plates  are  made  by  taking  advan- 
tage of  the  protective  action  of  gelatin,  which  pre- 
vents precipitation  of  the  silver  salt. 

The  therapeutic  agent,  collargol  is  a  colloidal 
silver  preparation,  in  which  albumin  acts  as  the 
protective  agent.  There  being  no  Ag  ions  it  is  not 
toxic;  bacterial  action,  however,  changes  it  to 
ordinary  silver  and  the  ions  act  antiseptically. 

Swelling  of  Colloids.  Many  plant  and  animal 
tissues,  also  other  gels  (as  starch,  agar,  gelatin,  and 
other  proteins)  have  the  power  of  taking  up  water, 
so  that  they  swell.  In  certain  optimum  concentra- 
tions acids  and  alkalies  increase  greatly  the  amount 
of  water  imbibed, 


CHAPTER   V 

FORMULAE    EMPIRICAL  AND  STRUCTURAL. 
ISOMERISM 

A  KNOWLEDGE  of  the  percentage  composition  and 
of  the  molecular  weight  of  a  substance,  as  we  have 
seen,  enables  us  to  assign  to  it  a  formula  indicating 
the  number  of  atoms  of  each  element  present  in 
the  molecule.  This  is  called  the  empirical  formula. 
But  it  often  happens  that  several  organic  substances 
with  very  different  properties  may  have  the  same 
empirical  formula.  For  example,  there  are  no  fewer 
than  eighty-two  compounds  having  the  empirical 
formula  CgHioOa.  Such  bodies  having  the  same 
empirical  formula  are  called  isomers.  It  is  evident, 
therefore,  that  a  more  detailed  formula  is  necessary 
—a  formula,  namely,  in  which  the  relations  of  the 
various  atoms  to  one  another  (i.e.,  the  grouping  of 
the  atoms)  are  indicated.  Such  a  formula  is  called 
the  structural  formula.  It  is  ascertained  by  acting 
on  the  substance  with  reagents  which  decompose 
it  into  simple  bodies  that  can  be  identified ;  in  other 
words,  we  must  tear  the  molecule  apart.  After 
some  knowledge  has  been  gained  as  to  what  simpler 
groups  of  atoms  the  body  is  composed  of,  an  attempt 
is  made  to  build  up  the  substance  by  causing  the 
simpler  groups  to  unite,  i.e.,  by  synthesizing  the  sub- 


FORMULA,  EMPIRICAL  AND  STRUCTURAL      99 

stance.     If  the  synthesis  is  successful,  the  structure 
of  the  molecule  is  proved. 

We  see  then  that  the  structural  formula  is  not 
only  a  graphical  expression  of  the  actual  number  of 
the  various  atoms  present  in  a  molecule  of  the  sub- 
stance, but  it  is  also  an  epitome  of  the  more  impor- 
tant reactions  of  the  substance. 

•In  the  chapters  that  immediately  follow  this  one, 
the  methods  by  which  the  various  facts  indicating 
the  structure  of  the  molecule  are  discovered  will  be 
fully  explained  (see  especially  acetic  acid,  p.  164). 
When  we  come  to  study  the  more  complex  sub- 
stances, we  shall  find  that  even  the  structural  for- 
mula does  not  always  suffice  to  differentiate  the  sub- 
stance, since,  indeed,  there  may  be  several  bodies 
having  the  same  structural  formula.  In  such  cases 
it  is  supposed  that  the  cause  of  the  difference  lies 
in  the  order  of  arrangement  of  the  atoms  in  space. 
This  subject  will  be  found  described  in  connection 
with  lactic  and  tartaric  acids  (pp.  214  and  222). 

Before  starting  with  a  systematic  study  of  the 
compounds  of  carbon,  the  student  should  bear  in 
mind  the  extreme  importance  of  the  structural 
formula;  he  should  never  allow  one  to  pass  him 
without  thoroughly  understanding  why  it  is  so 
written.  If  he  conscientiously  follows  this  advice, 
he  will  soon  find  that  organic  chemistry  is  by  no 
means  the  uninteresting  and  disconnected  subject 
so  many  students  think  it  to  be. 


100  ORGANIC  CHEMISTRY 


SYNOPSIS  OF  CHAPTERS  I-V. 

Determination  of  the  Chemical  Character  of  an  Organic 
Compound 

1.  PURIFICATION. 

a.  Methods. 

b.  Tests  of  purity. 

2.  IDENTIFICATION. 

a.  Physical  properties. 
6.  Elementary  analysis. 

3.  EMPIRICAL  FORMULA. 

a.  Elementary  analysis. 

b.  Molecular  weight  determination. 

4.  STRUCTURAL  FORMULA. 

a.  Reactions  to  detect  the  relative  placing  of  atoms 

and  groups  of  atoms  in  the  molecule. 

b,  Synthesis  of  the  molecule, 

Physical  Chemistry  Topics 

1.  Osmotic  pressure. 

2.  Electrolytic  dissociation. 

3.  Hydrolytic  dissociation. 

4.  Surface  tension. 

5.  Viscosity. 

6.  Colloids  (including  adsorption), 


CHAPTER   VI 

PRELIMINARY  SURVEY  OF  ORGANIC  CHEMISTRY 

BEFORE  attempting  to  study  the  various  organic 
substances  individually,  it  is  essential  that  we 
possess  a  general  idea  of  their  relationships  to  one 
another.  Their  number  is  so  great  that,  did  we 
attempt  to  remember  the  properties  and  reactions 
of  each  organic  substance  separately,  we  should 
utterly  fail,  and  should,  moreover,  probably  over- 
look one  of  their  most  important  characteristics  in 
contrast  with  inorganic  substances,  viz.,  their 
transmut ability  into  other  organic  compounds.  In 
inorganic  chemistry  it  is  impossible  to  convert  the 
compounds  of  one  element  into  those  of  another 
element,  except  by  substituting  the  elements.  Each 
element  has  its  own  fixed  chemical  properties  and 
compounds.  In  organic  chemistry,  on  the  other 
hand,  as  remarked  above,  we  may  consider  all  our 
substances  as  compounds  of  the  element  carbon  and 
as  being,  therefore,  convertible  into  one  another. 

As  is  natural,  we  select  as  our  basis  of  classifica- 
tion the  very  simplest  organic  substances,  namely, 
those  which  contain  carbon  along  with  one  other 
element.  From  our  studies  in  inorganic  chemistry 
we  know  that  there  are  several  elements  with  which 
carbon  may  be  thus  combined,  e.g.,  with  oxygen 
in  C02,  with  sulphur  in  C$2,  etc.  We  do  not,  how- 
ever, consider  these  as  organic  compounds,  the 

101 


102  ORGANIC  CHEMISTRY 

simplest  organic  compounds  being  those  in  which 
carbon  is  combined  with  hydrogen  or  with  nitrogen. 

In  union  with  nitrogen,  carbon  forms  cyanogen 
(which  is  the  lowest  member  of  a  group  of  com- 
pounds including  hydrocyanic  acid,  HCN,  cyanic 
acid,  HCNO,  sulphocyanic  acid,  HCNS)  and  the 
substituted  ammonias. 

-  In  union  with  hydrogen,  carbon  forms  the  so- 
called  hydrocarbons  (i.e.,  hydro[gen]  carbons).  Prac- 
tically all  the  remaining  carbon  compounds  may 
be  considered  as  derived  from  these. 

The  quantitative  relationship  between  C  and  H 
in  hydrocarbons  is  variable,  so  that  we  are  enabled 
to  subdivide  hydrocarbons  into  several  groups.  If 
we  express  the  hydrogen  in  terms  of  its  proportion 
to  carbon,  we  shall  find  that  all  the  hydrocarbons 
group  themselves  into  several  series,  four  of  which 
are  of  importance.  The  general  formulae  for  the 
four  series  or  groups  are  as  follows: 

(1)  CnH2n+2  (3)  CnH2ra-2 

(2)  CnH2ra  (4)  CnH2n_6 

(in  the  case  of  the  fourth  series  n  is  at  least  6.)         •-• 
It  will,  moreover,  be  found  that  it  is  to  the  first 
and  fourth  of  these  groups  that  the  great  majority 
of  hydrocarbons  belong. 

If,  now,  we  investigate  the  behavior  of  the  mem- 
bers of  these  four  groups  towards  hydrobromic 
acid,  we  shall  find  that  members  of  the  first  and 
fourth  groups  do  not  readily  react,  whereas  those 
of  the  second  and  third  do;  and  indeed,  that  these 
directly  combine  with  the  reagent  by  addition,  i.e., 


.  PRELIMINARY  SURVEY  103 

without  chemical  substitution.  We  may,  therefore, 
further  subdivide  our  four  groups  into  two,  viz., 
saturated  (1st  and  4th)  and  unsaturated  l  (2d  and  3d.) 

Of  the  two  saturated  groups  it  will  be  found  that 
many  members  of  the  4th  group  have  an  aromatic 
odor,  whereas  those  of  the  1st  do  not.  The  mem- 
bers of  the  4th  group  are  hence  often  styled  aromatic 
compounds,  and  on  account  of  the  fact  that  the 
members  of  the  1st  group  are  very  resistant  toward 
chemical  reagents,  they  are  called  paraffins  (parum 
affinis) . 

On  account  of  their  properties,  then,  we  may 
amplify  our  classification  into  paraffins  (1st  group), 
unsaturated  compounds  (2d  and  3d),  and  aromatic 
bodies  (4th).2  Compounds  of  the  first  three  groups 
make  up  the  ALIPHATIC  OR  FATTY  DIVISION  of  organic 
chemistry. 

The  compounds  and  derivatives  formed  by  the 
various  hydrocarbons  of  each  of  these  groups  are, 
in  general,  analogous,  although  the  reactions  by 
which  they  are  produced  may  differ  somewhat.  If 
we  understand  the  chemistry  of  the  most  important 
derivatives  of  one  hydrocarbon  in  each  group, 
we  shall  be  able  to  infer  approximately  what  the 
derivatives  and  reactions  of  all  the  other  members 
of  the  group  will  be;  and  further,  when  we  come  to 
study  the  hydrocarbons  of  the  other  groups,  we  shall 
find  many  of  their  compounds  quite  similar  to  those 
already  met  with. 

1  Only  unsaturated  compounds  can  form  addition  products. 

2  The  groups  are  also  sometimes  named  from  the  lowest 
member  of  each,  e.g.,   methane  group,   benzene  group,  etc. 


104  ORGANIC  CHEMISTRY 

From  these  preliminary  remarks  it  will  be  evident 
that  we  must  first  of  all  take  one  group,  and,  having 
shown  the  relationship  of  its  various  members  to 
one  another,  then  study  carefully  the  derivatives  of 
some  one  or  two  of  these  members. 

Let  us  take  the  paraffins.  They  have  the  general 
formula  CnH2n+2.  The  following  is  a  list  of  the  most 
important  members: 

Methane,  CH4  Butane,    C4Hio 

Ethane,    C2He  Pentane,  CsHi2 

Propane,  CsHs  Hexane,   CeHu 

It  will  be  noticed  that  each  differs  from  the  one 
preceding  it  by  CH2.  They  all  form  the  same  kind 
of  derivatives,  differing  from  one  another  again  by 
CBb;  thus  the  hydroxide  or  alcohol  of  methane  has 
the  formula  CH3OH,  and  of  ethane  C2H5OH. 
Such  a  series  is  called  an  homologous  series  (cf. 
nitrogen  oxides  series). 

Let  us  consider  why  it  should  be  that  the  increase 
of  complexity  is  by  CH2.  To  understand  this  we 
must  remember  that  C  is  considered  to  have  a 
valence  of  four;  that,  in  other  words,  an  atom  of 
it  can  combine  with  four  atoms  of  a  monovalent 
element  such  as  H,  and  that  each  of  these  valence 
bonds  has  exactly  the  same  combining  value.  We 
may  therefore  write  the  structural  formula  for 
methane  as  follows: 

H 


H— C— H. 


PRELIMINARY  SURVEY  105 

When  two  methane  molecules  fuse  together  a 
hydrogen  atom  of  each  disappears  and  the  liberated 
valence  bonds  unite  as  represented  in  the  formula 

H    H 

1       I 
H— C— C— H. 


Since  each  of  the  four  valence  bonds  of  C  has  the 
same  value,  it  will  be  obvious  that  only  one  propane 
can  exist:  that  we  can  write  only  one  structural 

H    H    H 

formula  for  it,  viz.,  H — C — G — C — H.    But  we  may 

H    H    H 

have  two  varieties  of  the  next  member  of  the  series, 
viz.,  butane,  for,  in  adding  an  extra  CH3  group  to 
propane,  we  may  add  it  either  to  the  central  C 
atom  of  the  chain  or  to  one  of  the  end  ones, 

H 

I 
HH— C— HH  H    H    H    H 

H— C- C C— H,    or    H— C— C— C— C— H 

III  I      I      I      I 

H        H        H  H    H    H    H 

and  the  properties  of  the  corresponding  body  will 
vary  accordingly;  in  other  words,  it  makes  a  differ- 
ence when  the  extra  CH3  group  is  tacked  on  to  a  C 
atom  in  union  with  two  H  atoms  (as  is  the  case 


106 


ORGANIC  CHEMISTRY 


with  the  central  atom),  and  when  on  to  one  with 
three  H  atoms  (as  in  the  case  of  an  end  atom). 
When  the  substitution  occurs  in  the  center  of  the 
chain  the  resulting  body  is  called  an  ^so-compound; 
when  at  the  end  it  is  normal.  Such  an  iso-compound 
therefore  contains  a  branched  chain.  Now,  this 
isomerism  applies  not  only  to  the  methyl  deriva- 
tives of  propane — for  butane  may  be  considered  as 
such — but  also  to  all  its  derivatives,  e.g.,  chlorides, 
hydroxides,  etc. 

By  using  models  instead  of  formulae  these  points 


Normal  butane 


Isobutane 


can  be  still  more  clearly  demonstrated:  thus  we 
may  consider  C  as  occupying  the  core  of  a  tetra- 
hedron (made  of  wood),  the  four  solid  angles  of 
which  represent  monovalent  combining  affinities, 
these  angles  being  covered  in  the  model  by  pyra- 
midal tin  caps  representing  H  atoms  (see  Fig.  22, 
p.  223).  By  removing  an  H  cap  from  two  models 
of  methane  and  joining  the  two  tetrahedra  by  the 


PRELIMINARY  SURVEY  107 

bared  angles,  we  obtain  the  model  of  ethane.  And, 
if  by  removing  another  H  cap  from  ethane  we 
unite  three  such  tetrahedra,  we  obtain  the  model 
of  propane.  It  does  not  matter  which  of  the  H 
caps  we  remove  in  these  manipulations;  the  result- 
ing ethane  or  propane  models  are  always  the  same. 
When  we  proceed  to  add  another  tetrahedron  to 
propane,  however,  it  will  be  evident  that  this  can 
be  done  in  either  of  two  ways,  by  attaching  it  either 
to  one  of  the  end  tetrahedra  or  to  the  central  one; 
in  the  former  case  Uie  model  will  represent  normal 
butane,  and  in  the  latter  isobutane;  and  so  with  the 
other  homologues. 

We  may  also  describe  this  progression  from  one 
hydrocarbon  to  the  next  higher  as  being  due  to 
the  replacement  of  the  H  atoms  of  the  former  by 
the  group  CH3,  called  methyl. 

Now  we  may  proceed  with  the  derivatives  of  the 
paraffins.  These  are  produced  by  the  replacement 
of  one  or  more  of  the  H  atoms  of  the  simple  hydro- 
carbons by  various  elements  or  groups  of  elements. 
Since,  as  explained,  these  derivatives  are,  in  general, 
the  same  for  each  member  of  a  series,  we  may  choose 
any  one  of  these  and  confine  our  attention  for  the 
present  to  its  derivatives,  remembering  always 
that  the  corresponding  derivative  of  any  other 
member  of  the  series  will  differ  from  it  by  just  as 
many  CH2  groups  as  did  the  original  hydrocarbons 
differ  from  one  another. 

In  inorganic  chemistry  t.v»^.  halogen  compounds,  * 
the  oxides,  and  the  hydroxides  are  among  the  most 
important  compounds  of  an  element,  and  the  same 


108  ORGANIC  CHEMISTRY 

applies  to  the  hydrocarbons:  each  has  halogen 
derivatives,  oxides  (ethers),  and  hydroxides  (al- 
cohols). Beyond  these,  however,  the  analogy  breaks 
down,  for  whereas  an  inorganic  hydroxide  is  an 
ultimate  product  and  cannot  be  further  oxidized, 
an  organic  hydroxide  (or  alcohol)  can  be  oxidized 
so  as  to  yield  various  substances  according  to  the 
extent  of  the  oxidation  and  the  nature  of  the  alco- 
hol started  with.  We  may,  therefore,  classify  our 
derivatives  thus: 

Halides. 

Oxides  or  ethers. 
Hydroxides  or  alcohols. 
Oxidation  products  of  alcohols. 

Halides.  When  the  paraffins  are  brought  into 
contact  with  chlorine,  substitution  of  one  or  more 
of  the  H  atoms  occurs.  Thus,  taking  methane, 
we  may  have  monochlormethane,  dichlormethane, 
trichlormethane  (chloroform),  and  tetrachlorme- 
thane.  In  connection  with  the  monohalogen  sub- 
stitution products  it  should  be  pointed  out  that 
they  may  be  considered  as  derived  from  a  halogen 
acid,  the  H  of  the  acid  having  been  replaced  by  a 
hydrocarbon  minus  one  of  its  H  atoms.  The 
general  term  for  all  such  groups  is  alky  I,  and  the 
specific  names  for  the  alkyls  are  methyl  (CH3-), 
ethyl  (C2H5-),  propyl  (CsHj-),  and  so  on.  An 
alkyl  is,  therefore,  analogous  with  a  monovalent 
element  or  with  NH4-. 

Halogen  atoms  may  likewise  displace  one  or  more 
of  the  H  atoms  of  the  alkyl  radicle  when  this  latter 


PRELIMINARY  SURVEY  109 

is  already  in  combination  with  some  other  substitut- 
ing group.  Thus,  chloral  is  trichloraldehyde, 
CC13CHO,  aldehyde  being  CH3CHO. 

Oxides  (or  ethers).  Since  oxygen  combines  with 
two  atoms  of  a  monovalent  element,  fas  in  sodium 
oxide,  Na2O,  the  lowest  alkyl  oxide  will  have  the 


formula          yO.     To  this  group  belong  the  ethers, 


25\ 

common  ether  being  XX 

/ 


Hydroxides  (or  alcohols)  .  When  one  of  the  H  atoms 
of  methane  is  replaced  by  hydroxyl,  OH,  methyl 

H 

I 
alcohol     is     formed.      Thus    H  —  C  —  H     becomes 

H 
H 

H  —  C  —  OH,  and  it  does  not  matter  which  of  the 

H 

H  atoms  is  thus  replaced,  the  resulting  compound 
being  always  the  same. 

The  same  is  true  for  ethane  and  its  alcohol,  ethyl 
alcohol,  CH3—  CH2OH. 

When  we  come  to  form  the  alcohol  from  propane, 
however,  we  encounter  conditions  analogous  with 
those  which  exist  when  butane  is  formed  from 
propane  (see  p.  106);  we  may  add  the  OH  group 
to  a  C  atom  of  propane  that  is  in  combination  with 
three  hydrogen  atoms  or  to  one  in  union  with  two 
such,  and  the  resulting  product,  as  we  have  seen, 


110  ORGANIC  CHEMISTRY 

will  exhibit  different  properties.  Consequently  we 
have  two  forms  of  propyl  alcohol.  Of  these  the  OH 
group  in  the  one  is  attached  at  the  end  of  the  chain, 
CH3— CH2— CH2OH;  in  the  other  it  is  attached 

OH 
in  the  middle  of  the  chain,  The 

CH3— CH— CH3. 

former  is  called  a  primary  alcohol,  the  latter  a 
secondary  alcohol. 

In  the  case  of  butane,  we  may  have  the  hydroxyl 
radicle  at  the  end  of  the  chain,  CH3 — CH2 — CH2 — 
CH2OH  (primary  butyl  alcohol);  or  attached  to  a 
C  atom  in  the  center  of  the  chain  with  one  other  H 

/OH 
atom  attached  to  it,  CH3 — CH2 — CH<f  (sec- 

M2l-a 

ondary   butyl   alcohol);    or — a   third   possibility — 
the  hydroxyl  radicle  may  be  attached  to  a  C  atom 
that  is  not  directly  combined  with  any  other  H 
CH3 

I 
atom,  thus  CH3 — C — OH    (tertiary  butyl  alcohol). 

CH3 

There  are,  therefore,  three  varieties  of  these 
alcohols : 

1.  Primary,   containing  the  group  — CH2OH 

2.  Secondary,  containing  the  group  — CHOH— 

3.  Tertiary,  containing  the  group       — C — OH 

The    essential    chemical    difference    between    these 

is  that  when  oxidized  they  yield  different  products. 

In  all  these  alcohols  only  one  hydroxyl  radicle  is 


PRELIMINARY  SURVEY  111 

present;  they  are  analogous  with  hydroxides  of 
monovalent  elements  such  as  sodium  (thus  NaOH  is 
analogous  with  CH3OH).  Just  as  in  inorganic 
chemistry,  however,  we  may  have  hydroxides  with 

-    /OH 

two   hydroxyls,    e.g.,    Ca<f        ,   so   may  we   have 

\OH 

alcohols  with  two  hydroxyls,  e.g.,  CH2 — OH.     Simi- 

CH2— OH 

larly,  there  are  alcohols  containing  three  hydroxyl 
CH2— OH 

groups,  e.g.,  CH  — OH,  which  are  analogous  with 

CH2— OH 
/OH 
Al^-OH. 
XOH 

Alcohols,  like  hydroxides  in  general,  have  the 
power  of  neutralizing  acids  to  form  salts.  Thus, 
sodium  hydroxide  reacts  with  HC1  in  accordance 
with  the  equation  NaOH+HCl  =  NaCl+H2O;  and 
taking  an  alkyl  hydroxide  (alcohol)  instead  of  an 
alkaline  hydroxide,  we  have  ROH+HC1=RC1  + 
H20  (R  =  alkyl).1  They  can  react  in  this  way  with 
organic  acids,  the  resulting  body  being  known  as 
an  ethereal  salt  or  ester  (see  p.  173).  These  organic 
salts  differ  widely  from  metallic  salts  in  their  chem- 
ical behavior. 

An  alcohol  with  only  one  hydroxyl  group  is  called 

1  Alcohols,  however,  are  not  really  basic  in  the  same  sense 
as  are  metallic  hydroxides. 


112  ORGANIC  CHEMISTRY 

monacid,1  because  it  can  react  with  only  one  molecule 
of  a  monobasic  acid;  those  with  two  such  groups 
are  called  diacid2  those  with  three  are  called  tri- 
acid.  The  monacid  alcohols  are  by  far  the  most 
numerous;  there  is  only  one  diacid  alcohol  (glycol) 
of  importance  and  one  triacid  alcohol  (glycerol). 

Oxidation  Products  of  Alcohols.  As  has  been  men- 
tioned (p.  110),  the  division  into  primary,  secondary, 
and  tertiary  alcohols  is  warranted  by  the  difference 
of  their  behavior  on  oxidation  : 

Primary  alcohols  yield  on  oxidation  aldehydes 

and  acids. 

Secondary  alcohols  yield  ketones. 
Tertiary  alcohols,  when  oxidized,  break  up 

into  lower  compounds. 

The  oxidation  products  that  we  must  consider 
are,  therefore,  aldehydes,  acids  and  ketones. 

A.  Aldehydes.     When  methyl  alcohol,  CH3OH,  is 

oxidized,  one  of  the  H  atoms  of  the  methyl  radicle 

becomes   replaced   by   hydroxyl,    so   that   a   body 

having  the  formula  CH2(OH)2  would  tend  to  be 

formed.     But  such  a  body  having  two  hydroxyls 

directly  attached  to  a  C  atom  cannot  exist,  and  it 

immediately   breaks   up,    giving    off   water,    thus: 

H 

I  /O|Hl,  leaving    a    body  having  the  formula 

• 


H  —  C^    .     This   is   an    aldehyde,  and   the  group 

1  The  terms  monatomic  and  monohydric  are  also  used;    but 
the  best  designation  would  be  monohydroxylic. 


PRELIMINARY  SURVEY  113 

—  C^     is  known  as  the  aldehyde  group.     The  CO 

portion  of  this    group    is    called    carbonyl.     Each 
hydrocarbon  has  a  corresponding  aldehyde. 

B.  Acids.  When  an  aldehyde  is  further  oxidized 
it  absorbs  oxygen  and  forms  a  body  having  the 
group  COOH,  which  is  called  the  carboxyl  group 
(from  carb[onyl  hydrjoxyl),  and  is  the  characteristic 
acid  group  of  organic  compounds: 

/H  /OH 

H—  C        +0=H—  C          . 


(Formic  aldehyde)  (Formic  acid) 

The  H  atom  of  this  carboxyl  group  can  be  replaced 
by  an  atom  of  a  monovalent  metal  to  form  a  salt, 
thus:  H-COONa,  sodium  formate.  Instead  of  a 
metal,  an  alcohol  radicle  may  replace  this  H  atom, 
the  resulting  compound  being  called  an  ethereal 
salt,  thus:  H  •  COOC2Hxj,  ethyl  formate.  Such  an 
acid  can  form  only  one  salt;  it  is  monobasic. 

If  two  carboxyl  groups  are  present,  the  resulting 
acid  is  dibasic.  The  lowest  dibasic  acid  corre- 
sponding to  the  simplest  diacid  alcohol  is  oxalic, 

COOH 
having  the  formula    |  Like  dibasic  acids  in 

COOH. 

general,  these  acids  can  form  two  series  of  salts,  in 
one  of  which  only  one  carboyxl  group  reacts, 
COOK 

(acid  potassium  oxalate),  and  in  the  other, 
COOH 


114  ORGANIC  CHEMISTRY 

COOK 

both,   |  (neutral  potassium  oxalate).     Tribasic 

COOK 
organic  acids  also  exist,  but  are  less  important. 

C.  Ketones.  When  a  secondary  alcohol  is 
oxidized,  it  forms  a  body  having  the  group  — CO — :, 
which  is  called  a  ketone: 

CH3— CHOH— CH3  +O  =  CH3— CO— CH3  +H20. 

(Secondary  propyl  alcohol)  (Acetone) 

OTHER  DERIVATIVES  OF  ALCOHOLS. 

The  hydroxy-acids  contain  one  or  more  hydroxyls 
besides  that  in  carboxyl. 

The  carbohydrates  are  complex  compounds  con- 
taining alcohol  groups.  Many  have  an  aldehyde  or 
ketone  group. 

THE  NITROGEN  DERIVATIVES  of  most  importance 
are  cyanogen  and  ammonia  compounds,  and  ni- 
trites. 

As  we  have  inorganic  cyanides,  as  KCN,  so  we 
have  organic  cyanides,  as  CH3  •  CN,  methyl  cyanide. 

There  are  several  kinds  of  ammonia  derivatives. 
One  hydrogen  atom  of  NH3  may  be  replaced  by 
an  organic  radicle,  leaving  the  group  NH2,  which  is 
called  the  amido-  or  amino-group.  Two  hydrogen 
atoms  may  be  displaced,  leaving  NH,  called  the 
imido-group.  All  three  hydrogen  atoms  may  be 
displaced,  leaving  only  N;  such  compounds  are 
called  tertiary  bases.  Or  we  may  have  the  hydrogens 
of  ammonium  (NEU)  in  NH^OH  displaced,  as  in 
the  quaternary  bases. 

Several  organic  nitrites  are  of  importance. 

The  ammo-acids  contain  both  the  NH2   and  the 


PRELIMINARY  SURVEY  115 

COOH  groups.    Acid  amides  have  the  OH  of  carb- 
oxyl  replaced  by  an  NEb  group. 

SULPHUR  DERIVATIVES.  In  these,  sulphur  may 
take  the  place  of  oxygen  in  an  alcohol  or  ether, 
giving  sulphur  alcohols-  (mercaptans),  as  CHsSH, 
and  sulphur  ethers,  as  CH3 — S — CH3. 

Sulphonic  acids  contain  the  group  SOsH  instead  of 
carboxyl. 

Finally,  UNSATURATED  HYDROCARBONS,  having  the 
linkings  C^C  and  C=C,  and  their  derivatives, 
will  conclude  the  chemistry  of  fatty  compounds. 

The  last  great  division  of  organic  chemistry,  that 
of  the  AROMATIC  OR  BENZENE  COMPOUNDS,  can  be 
considered  but  briefly  in  this  book, 

SYNOPSIS 

I.  Fatty  or  Aliphatic  Compounds. 

A.  SATURATED  HYDROCARBONS. 
Paraffins,  CnH2n+:. 
Paraffin  derivatives. 

1.  Halogen  substitution  products. 

2.  Oxides  or  ethers. 

3.  Hydroxides  or  alcohols,  and  derivatives. 

a.  Monacid  alcohols. 

1.  Primary  alcohols,  group — CH2OH. 

Oxidation    (  Aldehydes,  — CHO. 
products     ( Acids,  —COOH. 

2.  Secondary  alcohols,  — CHOH. 

Oxidation    (KetoneSj_co_. 
product       ( 

3.  Tertiary  alcohols,  — COH. 
6.  Diacid  alcohols. 

Oxidation  j  Aldehydes, 
products     { Acids. 


116  ORGANIC  CHEMISTRY 

c.  Triacid  to  hexacid  alcohols. 

Oxidation  j  Aldehydes, 
products     ( Acids. 

d.  Hydroxy-acids. 

e.  Carbohydrates. 

4.  Nitrogen  derivatives. 

a.  Cyanogen  combinations. 

b.  Ammonia    combinations    (amido-group, 
NH2;  imido-group,  NH,  etc.). 

c.  Nitrites. 

d.  Amino-acids,   acid   amides,   and   other 
similar  compounds. 

5.  Sulphur  derivatives. 
B.  UNSATURATED  HYDROCARBONS. 

1.  Ethylenes,  CKH2w  (— C=C— ). 

2.  Acetylenes,  CBH2n_2  (— C=C— ). 
C.1 

II."  Aromatic  Compounds.2 

A.  BEN/ENE  HYDROCARBONS,  CnH2n_6. 
Benzene  derivatives  (see  synopsis,  p.  423). 

1  As  will  be  explained  later,  the  group  of  cyclic  hydrocar- 
bons and  the  terpenes  (see  p.  309)  is  really  an  intermediate 
class  of  compounds  between  the  fatty  and  the  aromatic,  and  it 
would  naturally  be  inserted  in  the  synopsis  after  C.     To  avoid 
confusion  we  say  nothing  about  these  compounds  in  this  chapter. 

2  A    more    scientific    classification    of    organic    compounds 
groups  fatty  compounds  as  acyclic  (not  closed-chain  structure), 
benzene  derivatives  as  isocyclic   (closed  chain  of  C  atoms), 
and  certain  other  aromatic  compounds  as  heterocylic  (closed 
chain  in  which  N,  S,  or  0  takes  the  place  of  one  or  more  of  the 
C  atoms  of  the  chain). 


CHAPTER  VII 

SATURATED  HYDROCARBONS.    THE  METHANE 
SERIES. 

METHANE  (CKU)  can  be  synthesized  from  the 
elements  in  several  ways: 

(1)  A  small  quantity  of  CH*  can  be  produced 
directly  from  the  elements  by  passing  a  stream  of 
hydrogen  between  the  glowing  carbon  tips  of  an 
electric  arc-light  (see  acetylene,  p.  304). 

(2)  By  producing  carbon  disulphide   (€82)   and 
hydrogen  sulphide  (H2S),  and  allowing  a  mixture  of 
them  to  act  on  heated  copper: 

CS2  +2H2S  +8Cu  =  CH4  +4Cu2S. 

(3)  By  the  action  of  water  on  aluminium  carbide : 

AUC3+12HOH=3CH4+4A1(OH)3. 

THE  PARAFFINS  OR  MARSH-GAS  SERIES,  CnH2n+2. 

Having  obtained  methane,  we  may  build  up  the 
other  members  of  the  series  from  it  by  first  of  all 
producing  its  halogen  substitution  products  and 
then  reacting  on  these  with  metals,  thus : 

CHslI+Nal  +|Na+iiCH3  =CH3  •  CH3  +2NaI, 

• j         j M j 

(Methyl  iodide)  (Ethane) 

117 


118  ORGANIC  CHEMISTRY 

CH3  •  CH2  •  CH31+2NaI; 

(Methyl  iodide)  (Ethyl  iodide)  (Propane) 

also  with  zinc  methyl,  thus: 

2CH3|l+ZnkCH3)2  =  2CH3-CH3+ZnI2, 

(Zinc  methyl) 

CH2  -  CH3+ZnI2. 

The  paraffins  may  be  prepared  for  general  pur- 
poses (1)  by  decomposing  the  proper  substitution 
product  with  nascent  hydrogen,2  or  (2)  by  heating 
an  acid  derivative  with  an  excess  of  soda-lime: 

CH3I+2H=CH4+HI, 

(Methyl  iodide) 

CH3  •  COONa  +NaOH  =  CH4  +Na2C03. 

(Sodium  acetate) 

Methane  (marsh-gas),  CH4,  occurs  in  nature  (1) 
as  a  gas  arising  from  stagnant  water  where  decom- 
position of  vegetable  matter  is  going  on,  (2)  as  the 
so-called  fire-damp  in  coal-mines,  and  (3)  as  one  of 
the  constituents  of  natural  gas.  Its  production  by 
decomposition  of  vegetable  matter  can  be  brought 
about  in  the  laboratory  by  inoculating  water 
containing  small  suspended  pieces  of  filter-paper 

1  C2H6  and  C4Hi0  are  also  formed. 

2  The  nascent  hydrogen  for  such  reactions  as  this  may  be 
obtained  from  a  copper-zinc  couple  (made  by  heating  together 
one  part  of  powdered  copper  with  three  parts  of  powdered 
zinc  and  then  cooling  in  a  closed  vessel).     In  the  presence 
of  a  trace  of  acid  (H2S04)  the  couple  readily  yields  nascent 
hydrogen.    In  the  above  reaction  a  mixture  of  the  methyl 
iodide  with  alcohol  and  a  drop  of  H?S04  is  brought  into  contact 
with  the  couple,  drop  by  dropt 


SATURATED  HYDROCARBONS  119 

(cellulose)  with  the  microorganisms  contained  in 
sewage.  It  forms  an  explosive  mixture  with  air, 
hence  the  danger  of  having  bare  flames  in  coal- 
mines and  the  necessity  for  using  the  Davy  safety- 
lamp.  Fortunately  its -kindling  temperature  (i.e., 
the  temperature  at  which  it  explodes)  is  high. 

Natural  gas  has  about  95%  methane;  it  also 
contains  a  little  nitrogen,  ethane,  hydrogen  and 
only  a  trace  of  carbon  monoxide.  "There  are  two 
hypotheses  as  to  the  production  of  natural  gas,  one 
that  it  is  the  result  of  decomposition  of  vegetable 
or  animal  matter,  and  the  other  that  it  is  due  to  the 
action  of  water  on  metallic  carbides  (cf.  aluminium 
carbide  reaction).  Coal  gas  contains  30  to  40%  of 
methane. 

Water  gas  is  the  most  poisonous  illuminating  gas 
that  is  used,  because  of  its  large  content  of  carbon 
monoxide  (about  30%).  Coal  gas  is  also  very  dan- 
gerous, containing  4  to  10%  of  carbon  monoxide. 
This  poison  acts  by  combining  with  the  haemo- 
globin of  the  blood,  thus  interfering  with  the 
oxygen-carrying  power  of  the  blood.  The  water 
gas  prepared  from  crude  oil  and  steam  has  nearly 
the  same  composition  as  coal  gas.  Pintsch  gas 
(produced  from  oil)  contains  very  little  carbon 
monoxide,  but  a  large  amount  of  methane  and 
other  hydrocarbons. 

Methane  is  a  colorless,  odorless,  stable  gas. 
When  mixed  with  chlorine  and  exposed  to  direct 
sunlight  it  explodes: 

CH4+4C12=CC14+4HC1, 

(Carbon  tetrachloride) 


120  ORGANIC  CHEMISTRY 

or  when  exposed  to  diffused  sunlight  it  forms  a  mix- 
ture of  monochlor-  (CH3C1),  dichlor-  (CH2C12), 
trichlor-  (CHC13),  and  tetrachlor-methane  (CCU). 
The  last  is  also  called  carbon  tetrachloride. 

EXPERIMENT.  Dehydrate  some  sodium  acetate 
by  heating  it  in  an  evaporating  dish  with  a  small 
flame.  Cool,  powder  in  a  mortar  and  mix  10  gm. 
with  10  gm.  of  soda-lime,  and  heat  in  an  iron 
retort.  A  large  test-tube  could  be  used  instead  of 
a  retort.  By  means  of  a  delivery  tube  fitted  to 
the  retort,  collect  the  evolved  methane  over  water 
in  the  usual  manner.  Test  its  inflammability,  also 
its  lightness  compared  with  air. 

Ethane  (C2H6),  propane  (CsHs),  and  butane 
(CiHio)  are  also  gases  at  ordinary  temperatures. 
The  other  paraffins  are  liquids  or  solids,  Above 
butane  the  name  indicates  the  number  of  carbon 
atoms  in  the  formula.  There  is  a  regular  gradation 
of  physical  properties  from  the  lowest  to  the  highest 
members  of  the  paraffin  series:  the  boiling-point, 
the  specific  gravity,  and  the  melting-point  increase 
as  we  ascend  the  series. 

Boiling-point.  Specific  gravity.       Melting-point. 


Methane,  CH4  

-164° 

0.415  (at  -164°) 

-184° 

Ethane,  C2H6  

-  84.1° 

0.446  (at  0°) 

-172.1° 

Propane,  C3H8  

-  44.5° 

0.535    (atO°) 

-  45° 

Butane,  C4Hi0  

+     1° 

0.600    (atO°) 

Pentane,  C6Hi2  

36.3° 

0.627    (at  14°) 

Hexane,  C6Hi4  

69° 

0.6603  (at  20°) 

Tetradecane,  Ci4H3o 

252° 

0.775    (at  4°) 

4° 

Hexadecane,  Ci6H34. 

287° 

0.7758  (at  18°) 

18° 

Octodecane,  Ci8H38. 

317° 

0.777    (at  28°) 

28° 

SATURATED  HYDROCARBONS  121 

The  heat  of  combustion  of  a  gram  molecule  of  a 
paraffin  hydrocarbon  is  about  158  large  calories 
greater  than  that  of  the  next  lower  hydrocarbon; 
this  is  the  heat  of  combustion  value  of  the  CH2 
group. 

The  members  of  the  series  after  methane  are  met 
with  mainly  in  petroleum.  American  petroleum 
also  contains  a  few  sulphur  derivatives.  Cali- 
fornia petroleum  contains  some  benzene  hydro- 
carbons. To  secure  products  suitable  for  commer- 
cial purposes,  petroleum  is  subjected  to  crude 
fractional  distillation.  Some  of  the  oils  thus  ob- 
tained are  purified  by  successive  treatment  with 
sulphuric  acid,  caustic  soda  solution,  and  water. 
The  lower  fractions  are  distilled  with  steam;  the 
distillate  between  40°  and  150°  is  gasoline  (or 
naphtha),  and  that  between  150°  and  300°  is  kero- 
sene. Gasoline  and  its  products  are  mostly  mixtures 
of  CeHu,  CyHie,  and  CgHis.  From  low-boiling 
gasoline  there  can  be  obtained,  by  careful  frac- 
tional distillation,  cymogene  (a  gas),  rhigolene 
(b.  pt.  18.3°),  petroleum  ether  (40-70°),  gasoline 
(70-90°),  naphtha  (80-110°),  ligroin  (80-120°)  and 
benzine  (120-150°).  High-boiling  gasoline,  called 
also  benzine,1  is  used  as  a  solvent  in  many  industrial 
processes.  Kerosene  contains  the  paraffins  from 
C9H2o  to  CieH34.  It  should  contain  no  gasoline 
as  the  vapor  of  the  lower  hydrocarbons  in  a  lamp 
would  form  an  explosive  mixture  with  air.  Its 
flashing-point,  tested  in  a  manner  similar  to  that 
described  in  the  experiment  below,  tells  us  whether 

1  Carefully  distinguish  from  benzene  (p.  318). 


122  ORGANIC  CHEMISTRY 

it  contains  any  gasoline.  The  minimum  flashing- 
point  is  regulated  by  law,  varying  in  different  States 
and  countries  from  about  38°  to  49°.  The  residual 
tar,  after  kerosene  is  removed,  is  distilled.  By 
strongly  cooling  the  distillate  (paraffin  oil)  and 
filter-pressing  it,  crude  paraffin  is  separated;  and 
the  liquid  that  is  pressed  out  is  fractionally  dis- 
tilled (with  steam),  giving  the  various  grades  of 
lubricating  oil.  Purified  paraffin  is  a  white  waxy 
solid.  Vaseline  and  liquid  petrolatum  are  made 
by  a  special  process  from  selected  crude  oil.  Penn- 
sylvania petroleum  yields  16.5%  naphtha,  54% 
kerosene,  and  17%  lubricating  oils.  The  fuel  value 
of  gasoline  is  greater  than  that  of  an  equal  weight 
of  kerosene,  because  of  the  greater  percentage  of 
hydrogen  present. 

EXPERIMENT.  Place  the  flashing-point  apparatus 
(see  Fig.  18)  containing  20  c.c.  of  kero- 
sene in  a  large  beaker  two-thirds  full 
of  water.  Suspend  a  thermometer  so 
that  the  bulb  is  in  the  kerosene. 
Heat  the  beaker  slowly.  Bubble  air 
through  the  oil  at  frequent  intervals, 
and  test  the  vapor  with  a  lighted 
match.  Note  the  temperature  when 
the  vapor  takes  fire  (the  burning  tem- 
perature of  the  oil  is  40-50°  above 
FIG.  18.  the  flashing-point). 

There  are  many  isomers  of  the  paraffins  (see  p. 
106).  These  iso-compounds  are  represented  in  their 
formulae  as  having  branched  chains  of  carbon  atoms 


SATURATED  HYDROCARBONS  123 

instead  of  straight  chains  as  in  the  normal  com- 
pounds, and  they  possess  properties  quite  different 
from  those  of  the  normal  paraffins. 

Isobutane  is  the  iso-compound  having  the  fewest 
carbon  atoms  (see  p.  106) : 

CH3  •  CH2  •  CH2  -  CH3  ->  CH3  •  CH  -  CH3 

(Normal  butane) 

CH3 

(Isobutane) 

Isopentanes.     There  are  several  pentanes: 

CH3  •  CH2  •  CH2  •  CH2  •  CH3  \  CH3  •  CH  •  CH.2  •  CH3  j 

(Normal  pentane) 

CH3 

(Isopentane) 

CH3 

CH3— C— CH3 
CH3 

(Neopentane) 

The  newer  nomenclature  designates  these  isomers 
as  derivatives  of  methane;  thus,  isopentane  is 
dimethylethyl-methane,  and  neopentane  is  tetra- 
methy  1-met  hane . 

In  the  case  of  hexane  still  another  kind  of  iso- 
hydrocarbon  is  possible,  in  which  there  are  two 
branches  attached  to  different  (inside)  C  atoms  of 
the  chain. 


CHAPTER  VIII 

HALOGEN  SUBSTITUTION  PRODUCTS  OF  THE 
PARAFFINS 

IF  only  one  hydrogen  atom  of  the  hydrocarbon  is 
replaced  by  a  halogen  atom,  the  compound  is  called 
an  alkyl  halide  (or  alkyl  halogenide),  because  it  con- 
sists of  a  halogen  atom  linked  to  an  alkyl  radicle, 
e.g.,  CH3— Cl  (see  p.  108). 

The  alkyl  halides  derived  from  methane  are: 
methyl  chloride  or  monochlormethane,  CH3C1; 
methyl  bromide  or  monobrommethane,  CH3Br; 
methyl  iodide  or  monoiodomethane,  CH3I. 

General  Methods  of  Preparation.  (1)  The  chloride 
and  bromide  can  be  produced  from  methane  by 
mixing  chlorine  or  bromine  with  it  and  exposing 
the  mixture  to  diffused  sunlight. 

(2)  All  may  be   secured  by  acting  on   methyl 
alcohol  with  the  proper  halogen  acid,  in  accordance 
with  the  following  equations: 

CH3|OH+|[|C1  =CH3C1+H2O, 
CH3|OH+H|Br  =  CH3Br +H2O, 
CH3:OH+Hll  =CH3I  +H2O. 

(3)  Another  method  of  obtaining  them  is  by  the 
action  on  methyl  alcohol  of  PC13,  PBr3,  and  Pis: 

124 


HALOGEN  SUBSTITUTION  PRODUCTS  125 

3CH3OH+PC13  =  3CH3C1+P(OH)3, 
3CH3OH+PBr3  =  3CH3Br+P(OH)3, 
3CH3OH+PI3  =  3CH3I  +P(OH)3. 

In  a  manner  exactly  similar  to  the  last  two  methods 
the  ethyl  halides  can  be  derived  from  ethyl  alcohol. 

Some  of  the  More  Important  Alkyl  Halides. 

Methyl  chloride  (monochlormethane),  CH3C1,  is  a 
gas  under  ordinary  conditions.  It  is  readily  lique- 
fied, the  liquid  boiling  at  -23.7°. 

Ethyl  chloride  (monochlorethane),  C2H5C1,  is  a 
liquid  boiling  at  12.2°.  It  is  put  up  in  glass  or 
metal  tubes,  and  is  used  for  local  anaesthesia  by 
spraying  the  liquid  on  the  skin.  The  rapid  evapora- 
tion causes  the  abstraction  of  enough  heat  from  the 
skin  to  result  in  freezing  the  latter.  Its  vapor  is 
very  inflammable.  It  can  be  used  also  as  a  general 
anaesthetic,1  being  administered  as  a  vapor  by 
inhalation. 

Ethyl  bromide  (monobromethane),  C2H5Br,  is  a 
liquid  resembling  chloroform  in  odor,  density,  and 
physiological  effect.  It  boils  at  38.37°  (at  37.1°- 
37.4°  under  737  mm.  pressure),  and  its  specific 
gravity  is  1.468  at  13°.  It  may  be  obtained  by 
any  of  the  general  methods,  but  is  best  prepared  by 
the  action  of  ethyl  sulphuric  acid  on  -  potassium 
bromide,  as  in  the  following  experiment. 

1  In  this  book  brief  pharmacological  statements  are  fre- 
quent. For  full  information  on  these  points  consult  the 
excellent  pharmacology  text-books  by  Cushny  and  by  Sollmann. 


126 


ORGANIC  CHEMISTRY 


EXPERIMENT.  Into  a  250,  c.c  flask  put  55  c.c. 
of  concentrated  sulphuric  acid;  add  quickly  55  c.c. 
of  ethyl  alcohol,  shaking  at  the  same  time.  Cool 
the  flask  by  holding  it  in  running  water,  add  38  c.c. 
of  iced  water,  and  cool  again.  Meanwhile  set  up 
a  condenser  having  an  adapter  attached.  Use  a 
rapid  stream  of  water  in  the  condenser.  Put  into 
the  flask  50  gm.  of  powdered  potassium  bromide, 


FIG.  19. 

then  place  the  flask  on  a  sand-bath  and  attach  to  the 
condenser.  Fill  an  Erlenmeyer  flask  one-third 
full  of  ice-water  and  have  the  adapter  dip  below  the 
surface  of  the  water.  Place  this  receiving  flask  in 
a  bath  of  cold  water.  Heat  rapidly  and  continue 
heating  as  -long  as  any  distillate  comes  over. 
Watch  that  the  contents  of  the  receiver  be  not 
sucked  up  into  the  condenser.  If  this  is  threatened 
turn  the  adapter  so  that  air  can  enter  it. 

Decant  most  of  the  water  from  the  ethyl  bromide, 


HALOGEN  SUBSTITUTION  PRODUCTS  127 

then  add  ice-water  and  agitate.  Decant  the  water. 
Wash  several  times  in  this  manner.  Finally  shake 
the  washed  ethyl  bromide  with  a  dilute  sodium 
carbonate  solution;  do  not,  however,  cork  the  flask. 
Transfer  the  bromide  to  a  separating  funnel,  and 
run  out  the  bottom  layer  into  a  dry  flask.  Add 
dry  calcium  chloride,  cork  tightly,  and  let  it  stand 
in  a  cool  place.  After  a  day  or  so  distill  from  a 
small  fractionating  flask,  using  a  water-bath.  Place 
an  empty  receiving  flask  in  cold  water.  Note  the 
boiling-point.  Take  the  specific  gravity  in  a  small 
picnometer  holding  5  or  10  c.c.  The  following 
equations  will  explain  the  reactions: 

C2H5OH  +H2SO4  =  CH3  •  CH2  •  HSO4  +H2O, 

(Ethyl  alcohol)  (Ethyl  sulphuric  acid) 

CH3  •  CH2 ,  HS04  +KBr  =  CH3  •  CH2Br  +KHSO4. 

(Ethyl  bromide)        (Acid  potassium 
ilphate) 


sui 


Other  halogen  derivatives  (besides  the  alkyl  halides) 
are  illustrated  by  the  following  compounds :  dichlor- 
methane,  CH2C12;  dibrommethane,  CH2Br2;  diiodo- 
methane,  CH2I2;  trichlormethane,  CHC13;  tri- 
brommethane,  CHBr3;  triiodometnane,  CHI3;  and 
tetrachlormethane,  CC14. 

Of  the  many  compounds  thus  derived  from  the 
paraffins  the  three  trihalogen  substitution  products 
of  methane  are  the  only  ones  of  importance. 

Chloroform  (trichlormethane),  CHC13,  is  a  liquid 
having  a  pleasant  odor  and  a  sweetish  taste.  Its 
boiling-point  is  61  °  at  73 1  mm.  Its  specific  gravity  is 

1.498  at  15°,  1.5039  at  ii~-.     It  is  slightly  soluble  in 


128  ORGANIC  CHEMISTRY 

water,  one  liter  of  water  dissolving  8  gm.  of  chloro- 
form, while,  on  the  other  hand,  one  liter  of  chloro- 
form can  take  up  3  gm.  of  water.  It  is  a  good  solvent 
for  many  substances.  Chloroform  is  a  very  use- 
ful general  anaesthetic,  but  is  considered  much 
less  safe  than  ether.  Since  it  is  not  inflammable, 
it  can  be  used  at  night  as  an  anaesthetic  where  only 
lamp  or  gas-light  is  available.  Chloroform  vapor 
should  not  be  allowed  to  come  in  contact  with  a 
flame,  as  noxious  gases  are  produced.  It  is  not  a 
stable  compound,  as  exposure  to  light,  air,  and  mois- 
ture causes  some  decomposition,  thus  furnishing 
the  poisonous  impurities,  chlorine,  hydrochloric 
acid,  and  carbon  oxy chloride  or  phosgene  (COCU). 
These  impurities  can  be  readily  detected,  since 
chloroform  containing  them  gives  a  precipitate 
when  shaken  with  silver  nitrate  solution.  Pure 
chloroform  or  other  halogen  substitution  products 
do  not  immediately  give  a  precipitate  with  silver 
nitrate,  because  they  furnish  no  halogen  ions  (see 
p.  69).  The  addition  of  alcohol  to  chloroform, 
to  the  extent  of  0.6%,  prevents  decomposition. 
The  method  of  its  preparation  is  given  in  the  follow- 
ing experiment.  Chlorine  (from  bleaching-powder), 
acts  to  chlorinate  acetone,  and  from  the  product 
by  the  action  of  the  calcium  hydroxide  present  in 
the  mixture,  chloroform  is  produced.  Alcohol  may 
be  used  instead  of  acetone. 

EXPERIMENTS.  (1)  Preparation.  Into  a  liter 
flask  put  150  gm.  of  bleaching  powder  (calcium 
hypochlorite)  and  450  c.c.  of  water,  and  mix  them 


HALOGEN  SUBSTITUTION  PRODUCTS  129 

thoroughly.  Add  slowly  a  mixture  of  16  c.c.  of 
acetone  and  35  c.c.  of  water.  Connect  the  flask 
with  a  steam  generating  flask  and  with  a  condenser, 
as  for  steam  distillation  (p.  16).  Pass  steam  as 
long  as  droplets  of  chloroform  appear  with  the 
water  at  the  end  of  the  condenser.  Transfer  the 
distillate  to  a  separating  funnel,  draw  off  the  chloro- 
form and  wash  it  with  several  small  portions  of 
water.  Run  the  chloroform  into  a  dry  flask,  add 
calcium  chloride,  cork,  and  let  it  stand  a  day  or  so. 
As  the  yield  is  small,  it  need  not  be  redistilled,  but 
can  be  sealed  up  in  sample  bottles.  The  following 
equations  will  explain  the  reaction : 

CH3  •  CO  •  CH3  +6CI  =  CC13  •  CO  -  CH3  +3HC1, 

2CC13  •  CO  •  CH3  +Ca(OH)2  =  2CHC13 

+  (CH3-COO)2Ca. 

(2)  To  1  c.c.  of  chloroform  add  half  a  test-tube  of 
distilled  water  and  shake  vigorously.  Remove  the 
water  with  a  pipette.  Wash  three  times  in  this 
manner,  testing  the  last  wash-water  with  silver 
nitrate  solution;  if  no  precipitate  appears,  add  silver 
nitrate  to  the  washed  chloroform.  Let  it  stand, 
observing  whether  a  precipitate  forms  later. 

Bromoform  (tribrommethane),  CHBr3,  is  a  liquid 
which  boils  at  146°  at  751  mm.  On  cooling  it 
becomes  solid,  melting  at  8°.  Its  specific  gravity 
is  2.885  at  15°.  It  has  been  used  as  a  medicine. 

lodoform  (triiodomethane),  CHI3,  is  a  yellow 
crystalline  solid,  the  crystals  having  the  form  of 
hexagonal  plates.  Its  odor  is  peculiar  and  charac- 


130  ORGANIC  CHEMISTRY 

teristic.  It  melts  at  119°.  Its  specific  gravity  is 
4.008.  It  is  used  in  surgery  as  an  antiseptic,  the 
action  being  probably  due  to  iodine  which  is  freed. 
It  is  manufactured  from  acetone  by  the  action  of 
iodine  and  potassium  carbonate.  Its  method  of 
preparation  is  illustrated  in  the  following  experi- 
ment: 

EXPERIMENTS.  (1)  Dissolve  5  gm.  of  sodium 
carbonate  in  30  c.c.  of  warm  water,  add  5  c.c.  of 
alcohol,  heat  in  a  water-bath  to  70-80°,  and  add  a 
little  at  a  time  3  gm.  of  powdered  iodine,  shaking 
frequently.  If  the  liquid  has  become  brown,  add 
just  enough  sodium  carbonate  solution  to  change  it 
to  a  pale  yellow.  After  cooling,  filter  and  wash  the 
crystals.  After  being  dried  in  a  desiccator,  a  melt- 
ing-point determination  may  be  made. 

The  reactions  involved  are  doubtless  the  produc- 
tion of  iodal,  CIs-CHO,  by  the  action  of  NalO; 
then  the  conversion  of  iodal  by  the  action  of  the 
alkali  present  into  iodoform  and  sodium  formate. 

(2)  Make  a  yellow  solution  of  iodoform  in  alcohol, 
and  set  it  aside  loosely  covered;  by  slow  evaporation 
of  the  alcohol  hexagonal  crystals  of  considerable 
size  are  formed. 

This  reaction,  besides  being  given  by  alcohol,  is 
given  by  aldehyde,  acetone,  and  other  compounds 
that  contain  the  group  CH3  •  CO — ,  provided  the  CO 
is  not  part  of  a  carboxyl  group.  On  account  of 
its  characteristic  strong  odor,  the  production  of 
iodoform  in  this  manner  is  often  used  as  a  test  for 


HALOGEN  SUBSTITUTION  PRODUCTS          131 

the  presence  of  alcohol  or  other  substances  containing 
the  above  group. 

lodoform  Substitutes.  Because  of  the  unpleasant 
odor  of  iodoform  many  antiseptic  preparations  have 
been  put  on  the  market  which  disguise  or  eliminate 
the  bad  odor.  Such  are  eka-iodoform  (iodoform  with 
paraformaldehyde),  iodoformin  (iodoform  with  hexa- 
methylenetetramine),  iodoformogen  (protein  com- 
pound of  iodoform),  and  anozol  (iodoform  and 
thymol).  lodol  (see  p.  414)  and  possibly  aristol  (see 
p.  344)  liberate  iodine  in  the  tissues,  so  that  they  are 
suitable  substitutes  for  iodoform.  Diiodoform  is 
tetraiodoethylene,  C2l4  (see  ethylene,  p.  299). 

Tetraiodomethane,  Cl4,  is  a  solid,  having  a  very 
high  specific  gravity,  4.32. 

Similar  to  the  alkyl  halides  are  the  alkyl  combinations  with 
metals,  as  zinc  methyl,  Zn(CH3)2,  and  sodium  methyl,  NaCH3. 
Both  of  these  are  important  reagents. 


CHAPTER  IX 
ETHERS 

THE  alkyl  oxides  are  called  ethers.  They  con- 
sist of  two  organic  radicles  linked  to  an  oxygen  atom, 
as  methyl  ether,  CH3— O— CH3;  ethyl  ether, 

C2Hs O C2H5. 

A  general  method  of  synthesis  is  shown  by  the 
following  equations ; 


CH3-0  |Na+I|  CH3  =  CH3— O— CH3+NaI, 

(Sodium  methylate)     (Methyl  iodide)       (Methyl  ether) 


C2H5  -  OjNa +IiC2H5  =  C2H5— O— C2H5  +NaI. 

(Sodium  ethylate)       (Ethyl  iodide)      (Ethyl  ether) 

Methyl  ether  is  a  gas  and  is  unimportant. 

Ethyl  ether  is  common  ether.  Pure  ether  is  a 
liquid,  boiling  at  35°  (33.6°  at  734  mm.  barometric 
pressure)  and  having  a  specific  gravity  of  0.718  at 

25° 
15.6°  and  0.7079  at  ?L.    It  dissolves  to  a  certain 

extent  (about  6.5%)  in  water;  it  also  takes  up 
about  If  %  of  water.  If  ether  is  allowed  to  stand 
for  some  time  over  magnesium  bromide  both  water 
and  alcohol  will  be  abstracted  from  it  by  the  salt. 
To  obtain  absolute  ether,  it  is  necessary  to  treat 

132 


ETHERS  133 

the  ether  with  metallic  sodium  and  then  distill 
(Na  +H20  =  NaOH  +H) .  It  vaporizes  readily,  and, 
when  rapidly  evaporated,  abstracts  enough  heat  to 
freeze  water  if  the  latter  is  contained  in  a  small 
vessel  surrounded  by  •  the  ether.  The  vapor  is 
heavier  than  air  and  consequently  falls.  It  is 
very  inflammable,  and  should  therefore  be  kept 
away  from  a  flarne.  Ether  is  a  solvent  for  a  great 
number  of  substances.  It  is  extensively  used  as  an 
anaesthetic,  being  reasonably  safe  when  properly 
administered.  Heat  is  liberated  when  chloroform 
and  ether  are  mixed  in  certain  proportions. 

Because  of  the  use  of  sulphuric  acid  in  its  produc- 
tion, it  is  sometimes  called  sulphuric  ether.  To  pre- 
pare it,  ethyl  alcohol  is  allowed  to  flow  slowly  into 
heated  ethylsulphuric  acid  (see  p.  127)  contained  in 
a  flask.  The  following  experiment  will  make  clear 
how  this  is  done: 

EXPERIMENT.  In  a  liter  Jena  flask  mix  165  c.c. 
of  C.P.  H2SO4  with  210  c.c.  of  alcohol.  Fit  a  cork, 
pierced  with  three  holes,  into  the  mouth  of  the  flask, 
One  hole  is  to  admit  the  bent  tube  connecting  with 
the  condenser,  another  holds  a  thermometer,  and 
the  third  is  for  a  dropping  funnel  which  contains 
ethyl  alcohol.  The  bulb  of  the  thermometer  is 
immersed  in  the  liquid.  A  better  arrangement  is 
to  introduce  alcohol  into  the  ethylsulphuric  acid 
in  the  form  of  vapor.  For  this  it  is  necessary  to 
have  an  extra  flask  in  which  to  boil  alcohol,  which 
is  connected  with  a  tube  extending  to  the  bottom  of 
the  ether  generator  flask.  When  all  is  ready, 


134  ORGANIC  CHEMISTRY 

place  the  flask  on  a  sand-bath  and  connect  with  the 
condenser.  Submerge  the  receiving  flask  in  a  cold 
bath  and  use  .an  adapter  (cf.  ethyl  bromide,  p.  126). 
Heat  rapidly  until  the  ethylsulphuric  acid  has  a 
temperature  of  140°,  at  which  point  it  must  be  kept 
for  the  rest  of  the  process.  Run  in  a  very  little 
alcohol  from  the  funnel,  or  vapor  from  the  alcohol 
flask.  At  intervals,  i.e.,  when  the  amount  of  ether 
vapor  diminishes,  add  more  alcohol,  a  few  cubic 
centimeters  at  a  time.  Keep  flames  away  from 
the  vicinity  of  the  receiving  flask.  Watch  the 
apparatus  constantly.  When  sufficient  distillate 
has  been  secured,  wash  it  with  dilute  NaOH  solu- 
tion in  a  separating  funnel,  then  with  several  small 
portions  of  water;  draw  off  the  water,  pour  the 
ether  into  a  dry  flask,  add  calcium  chloride,  and 
cork  tightly.  Redistill  after  a  day  or  so,  using 
a  water-bath.  The  following  equations  will  explain 
the  reaction: 

C2H5OH  +H2S04  =  C2H5  •  HS04  +H2O, 

(Ethyl  alcohol)  (Ethylsulphuric  acid) 


C2H50  H  +  HS04:  •  C2H5=  C2H5— 0— C2H5+H2S04. 

(Ether) 

Mixed  ethers  contain  two  different  organic  radicles 
linked  to  the  same  oxygen  atom,  as  methyl  ethyl 
ether,  CH3 — O — C2H5.  They  may  be  formed  by  a 
synthetic  process  similar  to  that  described  above 
for  simple  ethers,  thus: 

CH3  •  O!Na+I:C2H6  =  CH3— 0— C2H5  +NaI. 


ETHERS  135 

It  is  interesting  to  note  that  the  boiling-point  of 
methyl  ethyl  ether  (11°)  is  intermediate  between  that 
of  dimethyl  ether,  (CH3)2O  (-23.6°),  and  that  of 
diethyl  ether,  (C2H5)20  (34.6°). 

The  ethers  are  very  stable,  not  being  affected  by 
boiling  with  alkali  or  dilute  acid. 


CHAPTER  X 

PRIMARY  ALCOHOLS 

AMONG  the  most  important  classes  of  organic  com- 
pounds are  the  alcohols.  The  empirical  formula  of 
a  monacid  alcohol  can  be  derived  from  the  formula  of 
the  paraffin  hydrocarbon  containing  the  same  num- 
ber of  carbon  atoms,  by  attaching  an  atom  of 
oxygen,  thus:  CnH2n+2O. 

Alcohols,  however,  are  not  oxides  of  the  hydro- 
carbons. They  are  hydroxides.  A  primary  alcohol 
is  an  alkyl  hydroxide.  Alcohols  cannot  be  obtained 
by  direct  oxidation  of  the  hydrocarbons.  That 
the  oxygen  atom  is  present  in  hydroxyl  is  proved  by 
the  following  reactions : 

(1)  CH3|OH +H|CI  =  CH3C1 +HOH 

(Methyl  alcohol)        (Methyl  chloride) 

(cf.   K|OH+H|CI =KCI+HOH), 

(2)  3CH3OH+PC13  =  3CH3C1+P(OH)3 

(Phosphorus  (Phosphorous 

trichloride)  acid) 

(cf.     3HOH+PC13=3HC1+P(OH)3), 

(3)  CH3OH  +H2S04  =  CH3HS04  +HOH 
(cf.     KOH  +H2S04  =KHS04  +HOH). 

(4)CH3OH+CH3-COOH=CH3-COO-CH3+HOH 

(Acetic  acid)  (Methyl  acetate) 

(cf.    KOH+CH3-COOH  =  CH3-COOK+HOH). 

136 


PRIMARY  ALCOHOLS  137 

The  striking  similarity  between  the  reactions  of 
alcohol  and  the  most  typical  of  all  hydroxides  (viz., 
KOH  and  H^O)  is  clearly  shown  by  these  reactions. 
The  reaction  of  potassium  and  sodium 1  with 
alcohols  shows  further  that  one  particular  hydrogen 
atom  of  the  latter  has  a  different  linking  from  that 
of  the  other  three  hydrogen  atoms : 

CH3OH  +Na  =  CH3ONa  +H 

(Sodium  methylate) 

(cf .         HOH  +Na  =  NaOH  +H) . 

Finally,  the  structure  of  an  alcohol  is  settled  be- 
yond a  doubt  by  its  synthesis  from  an  alkyl  halide 
by  the  action  of  a  strong  hydroxide : 

CH3]cT+K|OH  =  CH3OH  +KC1. 

Inorganic  hydroxides  are  strong  bases,  because 
they  furnish  many  hydroxyl  ions  when  dissolved  in 
water  (see  p.  172).  Alcohols,  on  the  other  hand, 
are  not  bases;  they  ionize  very  slightly,  if  at  all. 
It  is  to  be  noted  that  the  change  of  one  hydrogen 
atom  of  the  hydrocarbon  molecule  into  hydroxyl 
greatly  alters  the  chemical  behavior  of  the  com- 
pound; the  paraffin  is  very  stable  and  enters  into 
reaction  with  few  reagents,  whereas  the  alcohol 
is  reactive,  being  readily  affected  by  many  reagents. 
The  heat  of  combustion  of  an  alcohol  is  less  than 
that  of  the  corresponding  hydrocarbon.  This  is 
just  what  we  should  expect  since  there  is  oxygen 
in  the  alcohol  molecule. 

1  The  higher  alcohols  are  hardly  affected,  the  fewer  the  C 
atoms  in  the  alcohol  the  more  vigorous  is  the  sodium  action. 


138  ORGANIC  CHEMISTRY 


MONACID  PRIMARY  ALCOHOLS. 

These  comprise  the  most  important  group  of 
alcohols.  They  form  an  homologous  series  begin- 
ning with  methyl  alcohol.  There  is  a  regular  in- 
crease of  specific  gravity  and  boiling-point  from  the 
lowest  to  the  highest  members  of  the  series. 

Methyl  alcohol  (methanol,  carbinol),  H-CH2OH 
or  CHsOH,  is  obtained  from  the  distillate  produced 
by  the  destructive  distillation  of  wood  (see  p.  162). 
The  crude  alcohol  is  therefore  called  wood  alcohol. 
It  is  also  secured  by  destructive  distillation  of 
vinasse,  which  is  the  residue  left  after  ordinary 
alcohol  has  been  distilled  off  from  fermented  beet 
sugar  molasses. 

Fractional  distillation  does  not  suffice  to  free  the 
methyl  alcohol  from  the  acetic  acid,  acetone,  and 
other  constituents  of  crude  wood  spirits.  A  crys- 
talline compound,  methyl  oxalate  (CHs)2C2O4,  can 
be  formed  by  treatment  with  oxalic  acid.  The 
purified  crystals  can  then  be  decomposed  by  boiling 
with  ammonia  water,  yielding  pure  methyl  alcohol. 

If  the  crude  alcohol  be  treated  with  calcium 
chloride,  CaCU^CHsOH  is  formed;  this  is  not 
affected  by  heating  to  100°,  but  acetone  is  driven 
off.  Treatment  with  water  sets  the  alcohol  free, 
and  distillation  completes  the  purification. 

Methyl  alcohol  boils  at  66°  and  its  specific  gravity 

1  ^  A°  90° 

at  *±2-  is  0.7931  (at  ^  it  is  0.7913).     Its  melt- 
15.  o  4 

ing-point   is   higher   than   that    of   ethyl   alcohol, 
—  93.9°.    Electrolytes  dissolved  in  methyl  alcohol 


PRIMARY  ALCOHOLS  139 

ionize  readily.  It  mixes  readily  with  water,  exhibit- 
ing the  phenomena  of  contraction  of  volume  and 
liberation  of  heat.  It  is  a  useful  solvent;  in  con- 
sequence, the  crude  alcohol  is  used  in  the  prepara- 
tion of  paints.  It  is  intoxicating  if  taken  inter- 
nally; wood  alcohol  is  dangerous,  having  caused 
many  deaths  when  used  as  a  substitute  for  ethyl 
alcohol.  Wood  alcohol  burns  with  a  blue  flame, 
hence  its  use  in  alcohol  lamps. 

Ethyl  alcohol  (ethanol),  CH3-CH2OH  or  C2H5OH, 
is  common  alcohol.  Its  relation  to  methyl  alcohol 
is  seen  when  it  is  considered  as  methyl  alcohol 
in  which  one  hydrogen  atom  is  replaced  by  the 
methyl  radicle : 

H  •  CH2OH  ->  CH3  •  CH2OH. 

The  name  methyl  carbinol  expresses  this  relation. 
Similarly  the  higher  alcohols  are  called  carbinols 
(the  prefix  in  each  case  indicating  the  groups 
attached). 

Alcohol  is  produced  by  fermentation  of  .dextrose 
(glucose)  by  means  of  yeast. 

C6Hi206  =  2C02  +2CH3  •  CH2OH. 

(Dextrose) 

About  5%  of  the  dextrose  forms  by-products, 
such  as  amyl  alcohol,  glycerol  (i.e.,  glycerine),  and 
succinic  acid.  It  has  been  thought  that  lactic 
acid  is  an  intermediate  product  of  yeast  fermen- 
tation; and  that  it  is  converted  into  acetaldehyde 
and  formic  acid,  the  latter  in  turn  giving  up  H  (and 
evolving  C02),  which  adds  itself  to  the  aldehyde 


140  ORGANIC  CHEMISTRY 

molecule,  and  thus  ethyl  alcohol  results.  This 
theory  has  not  been  proved,  and  is  rather  discoun- 
tenanced by  the  fact  that  yeast  will  not  produce 
alcohol  from  lactic  acid,  nor  from  an  equimolecular 
mixture  of  formic  acid  and  acetaldehyde  (even  when 
these  are  gradually  set  free  in  the  reaction  mixture). 
Another  theory  advances  pyruvic  acid  as  the  first  in- 
termediate product  of  yeast  action.  No  theory  has 
as  yet  sufficient  experimental  evidence  in  its  favor. 
Alcoholic  beverages  are  obtained  by  fermentation 
of  fruit  juices  containing  sugar,  as  wine  from  grapes, 
or  of  malted  grain,  as  beer  from  barley.  Fermenta- 
tion is  inhibited  when  the  alcohol  content  reaches 
about  17%  (by  volume).  Malt  liquors  contain 
from  2  to  8%  of  alcohol.  Wines  contain  8  to  15%. 
Stronger  wines  are  made  from  these  by  adding 
alcohol.  Brandy  is  obtained  by  distillation  of  wine, 
whiskey  by  distillation  of  fermented  grain;  both  of 
these  contain  40  to  60%  of  alcohol  Many  liquors 
require  aging  in  order  that  the  by-products,  which 
are  disagreeable  and  injurious,  as  for  instance  fusel- 
oil,  may  be  converted  into  ethereal  compounds  of 
pleasant  taste  and  odor.  The  amount  of  alcohol 
present  in  a  liquor  can  be  readily  estimated  by 
distilling  100  c.c.  of  the  liquor  (diluted  with  50  c.c. 
of  water);  when  100  c.c.  of  distillate  has  been 
collected,  its  specific  gravity  is  determined.  The 
percentage  of  alcohol  is  found  by  referring  to  tables 
of  specific  gravities  (see  Appendix,  p.  445). 

Preparation.  Commercial  alcohol  is  made  from 
the  cheapest  forms  of  starch,  potato  or  corn.  The 
ground  or  mashed  raw  material  is  heated  until  the 


PRIMARY  ALCOHOLS  141 

starch  is  thoroughly  cooked.  After  cooling  malt 1 
is  added  and  the  mixture  is  kept  at  60-62°.  Malt 
contains  a  ferment,  diastase,  which  changes  starch 
into  the  sugar  maltose,  and,  to  the  extent  of  about 
20%,  into  dextrin.  The  sugar  solution  is  diluted, 
and  yeast  is  added. 

The  yeast  furnishes  a  ferment  that  splits  or  in- 
verts the  maltose  molecule  into  two  dextrose  mole- 
cules, and  also  a  ferment  that  decomposes  the  dex- 
trose into  alcohol  and  carbon  dioxide.  These 
ferments  can  be  extracted  from  the  yeast  cells  by 
grinding  the  latter  with  fine  quartz  sand,  subject- 
ing the  mass  to  a  very  high  pressure  (up  to  300 
atmospheres),  and  finally  filtering  the  extract 
through  porcelain.  This  filtrate  contains  no  yeast 
cells,  but  it  inverts  maJiosa^jnto  dextrose  and 
changes  dextrose  into  alcohol. 

The  ferment  in  this  extract  from  yeast  cells  is 
called  zymase.  Similar  intracellular  ferments  can 
be  obtained  from  certain  bacteria.  Ferments  are 
often  called  enzymes. 

The  weak  alcoholic  solution  (not  over  13%) 
obtained  by  this  process  of  fermentation  is  distilled 
in  an  apparatus  containing  a  fractionating  column. 
The  crude  distillate  (90%  alcohol)  is  filtered  through 
animal  charcoal,  which  removes  many  impurities. 
It  is  then  redistilled,  the  product  being  ordinary 
alcohol  (95%) .  This  is  apt  to  contain  some  aldehyde. 
The  strongest  alcohol  obtainable  by  the  most 
careful  fractionation  contains  4.5%  by  weight 

1  Malt  is  obtained  by  allowing  barley  to  germinate  to  a 
certain  stage. 


142  ORGANIC  CHEMISTRY 

of  water.  Commercial  absolute  alcohol  contains 
about  one-half  of  1%  of  water.  It  is  obtained  by 
digesting  alcohol  with  quick-lime  and  then  distilling 
(CaO+H2O=Ca(OH)2).  More  nearly  absolute 
alcohol  is  secured  by  treating  with  metallic  sodium 
and  distilling.  In  Europe  potatoes  are  used  for 
alcohol  production,  but  in  this  country  corn  starch 
is  the  material  used,  2.7  gallons  being  secured  from 
one  bushel  of  corn.  The  cost  of  the  process  of  manu- 
facture exclusive  of  the  cost  of  the  raw  material  is 
said  to  be  very  low,  less  than  five  cents  per  gallon. 

Properties.  Chemically  absolute  alcohol  is  almost 
unknown,  because  it  takes  up  moisture  so  rapidly 
when  exposed  to  the  air.  Absolute  alcohol  has  a 

1  ^  ^f\°  i  ^° 

specific  gravity  of  0.79365  at  ^§_,  0.79357  at  ^ 

lo.oo  4 

and  boils  at  78.3°  (corrected)  (at  734  mm.  pressure 
it  boils  at  77.7°).  It  solidifies  at  -112°.  It  has 
much  less  odor  than  common  alcohol.  Commercial 
absolute  alcohol  (dehydrated  alcohol)  contains  99% 
by  weight,  and  has  a  specific  gravity  of  0.798  at  15°. 
Alcohol  containing  95.57%  by  weight  has  the  lowest 
boiling-point  of  any  alcohol  preparation,  78.15°  at 
760  mm.  Alcohol  is  of  great  service  as  a  solvent. 
Alcohol  burns  with  a  colorless  flame.  When  mixed 
with  water,  rise  of  temperature  and  contraction  of 
volume  are  observed.  It  is  an  intoxicant;  the 
detrimental  effect  of  alcoholic  liquors,  however,  is 
due  in  part  to  other  compounds  besides  the  alcohol. 
Methylated  or  denatured  alcohol  is  alcohol  to  which 
wood  alcohol  or  nauseous  substances  have  been 
added  to  render  it  unfit  to  drink.  In  the  United 


PRIMARY  ALCOHOLS  143 

States  10  parts  of  wood  alcohol  and  1  or  2  parts  of 
benzine,  or  else  2  parts  of  wood  alcohol  and  1  or  2 
parts  of  crude  pyridine  per  100  parts  of  alcohol, 
are  used.  Such  alcohol  can  be  sold  duty-free  in 
many  countries. 

EXPERIMENT.  Into  a  large  bottle  or  flask  put 
500  c.c.  of  10%  glucose  solution,  and  add  some 
crumbled  yeast.  Through  a  cork  that  tightly  fits 
the  bottle  or  flask,  pass  a  glass  tube  bent  so  as  to 
extend  down  into  a  small  bottle  containing  some 
baryta  water,  the  tip  of  the  tube  jtist  reaching  the 
surface  of  the  latter;  through  a  second  hole  in  its 
cork  the  baryta  bottle  is  connected  with  a  tube  or 
tower  of  soda-lime.  Thus  C02  cannot  enter  the 
apparatus  from  without.  Let  it  stand  a  few  days, 
after  which  a  copious  precipitate  of  BaCOs  is 
obtained. 

Experiments  with  95%  alcohol.  (1)  Shake  10  c.c. 
in  a  test-tube  with  anhydrous  CuSO*  and  let  it 
stand  (corked)  one  hour;  the  CuSCX  becomes 
bluish  (with  absolute  alcohol  no  blue  color  appears). 
Explain  what  takes  place. 

(2)  Take  52  c.c.  of  alcohol  and  48  c.c.  of  water, 
each  being  at  a  temperature  of  20°,  mix  them  in  a 
100-c.c.  graduate,  and  note  the  maximum  tempera- 
ture, cool  to  20°,  and  read  off  the  volume  (about 
96.3  c.c.  instead  of  100  c.c.). 

When  miscible  liquids  are  mixed  a  change  in 
volume  is  generally  noticed,  usually  a  decrease 
(sometimes  an  increase).  Heat  may  be  either 
absorbed  or  given  off. 


144  ORGANIC  CHEMISTRY 

(3)  Put  10  c.c.  of  alcohol  in  a  test-tube,  and  add 
as  a  bottom  layer  5  c.c.  of  concentrated  sulphuric 
acid.  Throw  in  a  number  of  small  crystals  of  potas- 
sium permanganate.  Flashes  of  fire  will  occur  in 
the  liquid  in  the  zone  of  contact  of  the  alcohol  and 
acid  (probably  due  to  ozone  production,  and  intense 
oxidation  of  a  derivative  of  alcohol). 

Propyl  alcohol  is  a  primary  alcohol  having  the 
formula,  CH3  -  CH2  -  CH2OH. 

Normal  butyl  alcohol  is  CH3-CH2-CH2-CH2OH. 
Primary  isobutyl  alcohol  is  CH3-CH-CH2OH. 

I 

CH3 

As  with  hydrocarbons  the  branching  of  the  chain 
lowers  the  boiling-point. 
Normal  amyl  alcohol  is 

CH3  •  CH2  •  CH2  •  CH2  •  CH2OH. 

Primary  isoamyl  alcohol,  called  isobutyl  carbinol,  is 
CH3  •  CH  •  CH2  •  CH2OH ;  this  is  the  main  constituent 

CH3 

of  fermentation  amyl  alcohol.  Both  of  these  amyl 
alcohols  are  contained  in  fusel-oil  and  in  certain 
liquors,  especially  recently  distilled  brandy  and 
whiskey.  There  are  three  isoamyl  alcohols  having 
the  same  structural  formula, 

CHav/H 

CH3-CH2/    \CH2OH. 

Their  chemical  and  physical  properties  are  identical, 
except  that  their  action  on  polarized  light  is  different. 


PRIMARY  ALCOHOLS  145 

One  rotates  the  beam  of  light  to  the  left,  another 
rotates  it  to  the  right  —  these  are  the  active  amyl  alco- 
hols; the  third  does  not  cause  rotation  and  is  called 
inactive  amyl  alcohol.1  There  is  also  another  amyl 
alcohol  containing  the  primary  alcohol  group, 

CH3\     /CH3 
CH3/     \CH2OH. 

There   are   four   secondary   amyl    alcohols,    two 
normal  and  two  isoamyl  alcohols. 
There  is  a  tertiary  isoamyl  alcohol 


v      / 
/     \ 


OH 


CH3/     \CH2—  CH3, 

which  has  been  used  as  a  hypnotic  under  the  name 
amylene  hydrate. 

Fusel  oil  contains  normal  propyl  alcohol,  primary 
isobutyl  alcohol,  primary  isoamyl  alcohol  and  the 
optically  active  (primary)  isoamyl  alcohol. 

Solubility  of  alcohols.  The  hydroxyl  group  tends 
to  render  a  compound  soluble  in  water;  the  fewer 
the  carbon  ,atoms  the  more  soluble  the  alcohol. 
Methyl,  ethyl  and  propyl  alcohols  mix  with  water 
readily,  while  30  parts  of  butyl  alcohol  and  only  6 
parts  of  amyl  alcohol  dissolve  in  100  parts  of  water. 
1  For  a  discussion  of  this  form  of  isomerism,  see  p.  214. 


CHAPTER  XI 

ALDEHYDES 

IF  a  primary  alcohol  be  oxidized,  the  first  product 
is  an  aldehyde: 

CH3  •  CH2OH  +0  =  CH3  •  CHO  +H20. 

Two  atoms  of  hydrogen  have  been  removed  from 
the  alcohol  molecule,  hence  the  name  al(cohol) 
dehyd(rogenatus) .  The  reaction  is  more  accurately 
indicated  as  follows : 

CH3  •  CH2OH  +0  =  CH3  -  CH 

°bll 

Two  hydroxyls  become  attached  to  the  same  car- 
bon atom,  but,  as  is  the  rule  1  in  organic  compounds, 
such  a  combination  is  too  unstable  to  persist  and  H20 
splits  off. 

It  is  to  be  noticed  that  the  aldehyde  group — CHO 
contains  no  hydroxyl.  This  can  be  proved  experi- 
mentally. If  alcohol  or  any  other  hydroxyl-contain- 
ing  compound  be  treated  with  phosphorus  penta- 
chloride,  the  place  of  each  hydroxyl  group  is  taken 
by  one  chlorine  atom: 

CH3  •  CH2OH  +PC15  =  CH3  -  CH2C1 +POC13  +HC1. 

1  There  are  three  well-known  exceptions  to  this  rule — chloral 
hydrate,  mesoxalic  and  glyoxylic  acid. 

146 


ALDEHYDES  147 

But  if  an  aldehyde  is  similarly  treated,  a  dichlor-com- 
pound  is  obtained: 

CH3  •  CHO  +PC15  =  CH3  •  CHC12  +POC13. 

Therefore  the  aldehyde  group  must  be  written  CHO, 
or  CO  •  H.  Nascent  hydrogen  converts  an  aldehyde 
into  the  corresponding  primary  alcohol. 

The  aldehydes  are  named  from  the  acids  they 
produce  when  oxidized:  thus,  H-CHO  is  formic 
aldehyde  or  formaldehyde,  and  CH3-CHO  is  acetic 
aldehyde  or  acetaldehyde. 

Aldehyde  reactions.  (1)  All  aldehydes  are  strong 
reducing  agents,  because  they  readily  take  up 
oxygen  to  form  acids.  The  common  tests  for  sugar 
are  really  aldehyde  reactions,  as  practically  all 
sugars  contain  the  CHO  group.  The  reduction  of 
silver  and  copper  salts  is  illustrated  by  the  experi- 
ment below. 

(2)  The  linking  C— 0  in  the  aldehyde  group  causes 
aldehydes  to  act  like  unsaturated  compounds,  for 
they  readily  form  addition  compounds,  thus: 


,0  /0-H 

CH3—  C<     +HCN=CH3—  C^  -  CN, 
XH  \H 

(Acetaldehyde)  (Acetaldehyde  cyanhydrin) 

.0  /0-H 

CH3—  Cf     +NH3=CH3—  C(-  -  NH2, 
X 


H  \H 

(Aldehyde  ammonia) 


.0  X0— H 

CH3— Cf     +NaHS03=CH3— Ce S03Na. 

XH  \H 

(Sodium  acid  sulphite)  (Aldehyde  bisulphite) 


148  ORGANIC  CHEMISTRY 

(3)  Phenylhydrazine  can  combine  with  an  alde- 
hyde  by  removing   O   of  the   carbonyl  group,    a 
hydrazone  being  formed. 

(4)  Aldehydes  (except  chloral  hydrate)  cause  a 
violet-red  color  to  appear  when  added  to  a  solution 
of  fuchsin  which  has  been  decolorized  by  sulphurous 
acid.     This  reaction  is  due  to  the  formation  of  con- 
densation products    (see   acetaldehyde).     Dextrose 
does  not  give  this  test  because,  as  in  the  case  of 
chloral  hydrate,  it  does  not  contain  a  C  =O  group; 
however,  in  the  case  of  both  of  these  compounds  the 
aldehyde  character  appears  under  the  influence  of  the 
strong  reagents  (and  the  heat)  used  for  other  tests. 

Formaldehyde  (methanal),  H-CHO,  is  a  gas.  It 
is  very  soluble  in  water.  Commercial  formalin  is  a 
40%  solution.  Formaldehyde  is  prepared  by  bub- 
bling air  through  methyl  alcohol,  which  is  kept  at 
about  50°;  then  the  mixture  of  air  and  vapor  is 
passed  through  a  heated  tube  containing  platinized 
asbestos:  H-CH2OH+0=H.CHO+H2O.  .  It  is 
also  produced  by  burning  methyl  alcohol  in  a  special 
lamp  in  which  the  supply  of  air  is  limited,  so  that 
incomplete  combustion  occurs;  part  of  the  alcohol 
is  oxidized  to  formaldehyde  and  escapes.  This 
lamp  can  be  used  for  disinfection  of  rooms,  but  is 
not  very  satisfactory. 

Formaldehyde  has  a  tendency  to  form  polymers. 
A  polymer  has  a  molecular  weight  which  is  an  even 
multiple  of  that  of  the  original  substance,  and  it 
has  the  same  percentage  composition  as  the  lat- 
ter. Thus  paraformaldehyde  (trioxymethylene)  is 
(H  •  CHO)s.  Its  graphic  representation  is 


ALDEHYDES  149 

H 

I/H 
C/ 


o        o 

0— (X 


H'   |  NH 

H          H 

Paraformaldehyde  (paraform)  is  a  white  sub- 
stance, which,  on  being  heated,  is  converted  into 
formaldehyde.  It  is  sold  in  the  form  of  tablets 
or  candles  for  disinfecting  purposes. 

With  ammonia,  formaldehyde  does  not  form  a 
simple  addition  compound  as  do  other  aldehydes, 
but  a  complex  substance,  hexamethylentetramine 
(see  p.  264). 

Formaldehyde  is  an  efficient  germicide,  and  is 
therefore  used  extensively  for  disinfecting  pur- 
poses. It  is  used  either  as  the  gas  or  in  dilute  solu- 
tion. It  is  very  irritating  to  the  eyes  and  mucous 
membranes.  The  dilute  solution  also  hardens  al- 
buminous substances,  and  is  consequently  used  to 
prepare  tissues  for  histological  examination.  It 
converts  a  solution  of  gelatin  into  a  hard  insoluble 
mass. 

Glutol  is  a  substance  produced  by  the  action  of 
formaldehyde  on  gelatin.  In  the  form  of  a 
dry  powder  it  is  used  as  a  surgical  dressing  for  raw 
surfaces.  It  is  said  to  act  as  an  antiseptic  because 
of  slow  liberation  of  formaldehyde. 


150  ORGANIC  CHEMISTRY 

EXPERIMENTS.  (1)  To  a  few  cubic  centimeters  of 
concentrated  H2S04  in  a  test-tube  add  a  few  drops  of 
ferric  chloride  solution;  with  a  pipette  run  in  about 
5  c.c.  of  milk  containing  5  drops  of  1  :  5000  for- 
maldehyde solution  as  a  top  layer,  avoiding  mixing 
with  the  H2S04.  A  violet  zone  forms  between  the 
two  layers. 

(2)  Set    in    a    desiccator    an    evaporating    dish 
containing  5  c.c.  of  formalin.     Leave  several  days 
until  a  white  solid,  paraformaldehyde,  is  obtained. 
When  this  is  secured,  heat  some  of  it  in  a  dry  test- 
tube.     It  volatilizes  completely,  passing  away  as 
formaldehyde    gas.     Note    the    odor.     Be    careful 
not  to  get  strong  fumes  into  the  eyes  or  nostrils,  as 
the  gas  is  very  irritating. 

(3)  To  10  c.c.  of  milk  in  a  large  evaporating  dish 
add  a  little  formaldehyde  and  10  c.c.  of  concentrated 
hydrochloric  acid  containing  one  drop  of  5%  ferric 
chloride.     Heat  over  the  flame,  holding  the  dish  in 
the  hand  and  maintaining  a  rotary  motion."    At 
about  90°  the  mixture  acquires  a  violet  color. 

(4)  Add  4  drops  of  methyl  alcohol  to  3  c.c.  of 
water  in  a  test-tube.     Make  a  spiral  of  copper  wire 
that  will  easily  slip  into  the  tube.     Heat  the  wire 
until  red  hot  and  plunge  it  into  the  solution.     Re- 
peat this  several  times.     Cool  the  liquid,  add  1  drop 
of  0.5%  resorcinol  solution,  and  with  a  pipette  run 
in  a  bottom  layer  of  5  c.c.  of  concentrated  sul- 
phuric acid.     A  red  zone  develops.     Why  is  for- 
maldehyde   produced    by    this    procedure?    This 
is  used  as  a  test  for  small  quantities  of  methyl 
alcohol. 


ALDEHYDES  151 

Acetaldehyde  (ethanal,  aldehyde),  CH3-CHO,  can 
be  obtained  in  similar  manner  as  formaldehyde 
by  the  oxidation  of  ethyl  alcohol  vapor,  induced 
by  heated  platinum.  The  oxidation  is  generally 
effected,  however,  by  the  use  of  sulphuric  acid  and 
sodium  or  potassium  dichromate,  as  described 
in  the  experiment  below.  Acetaldehyde  boils  at 
20.8°  and  has  a  specific  gravity  of  0.780  at  20°. 

Acetaldehyde  can  be  changed  into  the  polym- 
ers, paraldehyde,  a  liquid  boiling  at  124°,  and 
metaldehyde,  a  solid.  Both  have  the  formula 
(CH3-CHO)3.  It  is  supposed  that  the  difference 
in  their  structural  formulae  is  a  stereomeric  dif- 
ference (see  p.  214),  that  is,  a  difference  in  the 
arrangement  in  space  of  a  CH3  group  in  relation  to 
the  rest  of  the  molecule.  Paraldehyde  is  a  hypnotic. 

Aldehyde  molecules  can  be  made  to  fuse  together, 
forming  a  "  condensation  "  product,  aldol.  Zinc 
chloride  will  effect  this  change: 


O—  H 
2CH3—  CH  -*  CH3—  CH—  CH 


—  C 


It  has  been  suggested  that  the  production  of 
starch  and  sugar  by  plants  is  due  to  condensation 
and  polymerization  of  formaldehyde,  the  latter 
being  synthesized  from  C02  and  EbO.  A  sugar 
can  be  made  from  formaldehyde  by  condensation 
under  the  influence  of  lime-water  (see  p.  232). 

EXPERIMENTS.  Preparation.  (1)  Mix  in  a  large 
flask  100  c.c.  of  water  and  30  c.c.  of  C.P.  H2S04. 


152 


ORGANIC  CHEMISTRY 


Fit  a  cork  having  two  holes,  one  for  the  bent  tube 
connecting  with  a  condenser,  the  other  for  a  drop- 
ping funnel.  Have  the  tip  of  the  dropping  fun- 
nel about  3  cm.  above  the  liquid.  Connect  with 
the  condenser,  and  place  the  receiving  flask  in 
ice-water.  Heat  the  flask  over  wire  gauze  to  the 
boiling-point.  Now  add  through  the  funnel,  in 
a  slow  stream,  a  solution  of  sodium  dichromate 
(100  gm.  of  dichromate  dissolved  in  100  c.c.  of  water, 


FIG.  20. 

and  mixed  with  53  c.c.  of  alcohol).  Remove  the 
flame  as  soon  as  distillation  is  well  started.  If 
vapor  passes  through  uncondensed,  slacken  the 
stream.  If  aldehyde  ceases  distilling,  heat  again 
with  the  flame.  When  all  of  the  solution  has  been 
added,  redistill  the  distillate.  Save  a  portion  of 
the  crude  distillate  for  making  the  aldehyde  tests 
given  below.  In  redistilling  tilt  the  condenser 
upward,  as  shown  in  the  diagram.  Circulate 
through  it  water  heated  to  30°,  using  a  reservoir  or 
large  funnel.  Connect  the  condenser  with  a  drop- 


ALDEHYDES  153 

ping  funnel,  which  dips  into  the  ether  in  the  first 
wash-bottle.  Put  25  c.c.  of  dry  ether  into  each 
wash-bottle.  As  aldehyde  will  not  condense  at 
30  °,  while  most  of  the  alcohol  and  water  will,  only 
aldehyde  passes  into  the  ether,  which  absorbs  it. 
Keep  the  ether  bottles  in  a  bath  of  ice-water.  When 
the  aldehyde  seems  to  have  all  passed  over,  trans- 
fer the  ether  to  a  beaker,  which  is  placed  in  a  freezing- 
mixture.  Now  bubble  into  it  ammonia  gas  (se- 
cured by  heating  NH4OH  in  a  flask),  which  has  been 
dried  by  passing  through  a  tower  of  soda-lime. 
A  mass  of  white  crystals  of  aldehyde  ammonia  will 
finally  appear.  Filter,  wash  the  crystals  with  ether, 
and  let  them  dry.  From  this  product  pure  alde- 
hyde may  be  obtained  by  dissolving  some  of  it  in 
an  equal  weight  of  water,  adding  3|  times  as  much 
50%  H2S04,  and  then  distilling.  Put  some  of 
the  crystals  in  a  sample  bottle,  hold  the  bottle 
obliquely,  bottom  up,  and  fill  with  ammonia  gas; 
cork  and  seal  with  sealing  wax. 


Na2Cr207  +4H2S04  =  3O  +Cr2(S04)3 

+4H20, 

CH3-CH2OH+0=CH3-CHO+H20, 


CH3  •  CHO  +NH3  =  CH3 

NH 

(2)  Aldehyde  tests,  (a)  Add  a  little  of  the  crude 
distillate  to  5  c.c.  of  dilute  Fehling's  solution  in  a 
test-tube;  boil  until  Cu2O  is  precipitated. 

(6)  Add  another  small  portion  to  a  few  cubic 
centimeters  of  ammoniacal  AgNO3  solution  in  a 


154  ORGANIC  CHEMISTRY 

perfectly  clean  test-tube;  and  heat  gradually.  A 
mirror  of  silver  is  deposited. 

(c)  To  1  c.c.  of  dilute  rosaniline  (fuchsin)  solution 
add  a  solution  of  sulphurous  acid  until  almost  decol- 
orized. Add  some  aldehyde  solution  and  shake,  a 
violet-red  color  appears.  Schiff's  reagent  is  very 
convenient  to  use  for  this  test.1 

Chloral  (trichloraldehyde),  CC13-CHO,  is  a  chlor- 
ine derivative  of  acetaldehyde.  It  is  produced 
by  passing  dried  chlorine  gas  into  absolute  alcohol 
for  several  days.  Aldehyde  and  HC1  are  the  first 
products  of  the  chlorination.  The  final  product 

X)C2H5 

is  chloral  alcoholate,  CCls  •  CH\  ,  an   addi- 

^ 


tion  compound  of  chloral  with  alcohol.  Chloral 
is  liberated  from  this  by  the  action  of  concentrated 
sulphuric  acid. 

Chloral  is  an  oily  liquid,  boiling  at  97.7°  and  hav- 
ing a  specific  gravity  of  1.512  at  20°.  It  gives  the 
aldehyde  reactions.  When  it  comes  into  contact 
with  water  it  forms  chloral  hydrate  crystals. 

/H 
Chloral    hydrate,    CCl3-Cr-OH,    is     believed    to 

XOH 

have  two  hydroxyls  attached  to  the  same  carbon 
atom,  contrary  to  the  general  rule.  It  may  be 
considered  an  addition  compound  of  the  aldehyde 
with  water.  One  reason  for  believing  that  a  typical 

1  Prepare  the  reagent  by  saturating  with  S02  gas  a  solution 
of  2.2  gm.  of  rosaniline  in  10  c.c.  of  water.  Cork  tightly  and 
let  it  stand  until  light  yellow  or  colorless.  Dilute  with  200  c.c. 
of  water  and  keep  in  a  dark-colored  bottle  well  stoppered. 


ALDEHYDES  155 

CHO  group  is  not  contained  in  it  is  the  fact  that 
it  does  not  give  the  fuchsin  test. 

Chloral  hydrate  is  extremely  valuable  as  a 
medicine,  being  used  as  a  hypnotic.  It  is  very 
soluble  in  water  and  in  -alcohol.  It  melts  at  57°. 
Alkaline  solutions  decompose  both  chloral  and 
chloral  hydrate  to  chloroform  and  formic  acid: 

CC13  •  CHO  +KOH  =  CC13H  +HCOOK. 

(Potassium  formate) 

EXPERIMENTS.  (1)  Try  the  aldehyde  tests  (see 
acetaldehyde)  with  a  solution  of  chloral  hydrate. 

(2)  Warm   a  few   cubic   centimeters   of    chloral 
hydrate  solution;    after  adding  NaOH,  notice  the 
odor  of  chloroform. 

(3)  Boil  a  few  cubic  centimeters  of  chloral  hydrate 
solution;  then  test  part  of  it  with  AgNOs;  it  gives 
no  precipitate.     Now  add  some  zinc  powder  to  the 
original    solution    and   boil    two    minutes.     Filter; 
test  the  filtrate  with  AgN03;   it  gives  a  white  pre- 
cipitate   of    AgCl.     The    zinc    decomposes    water; 
the    nascent    hydrogen    produced    takes    chlorine 
from  the  chloral  hydrate,  forming  HC1  (which  com- 
bines with  the  zinc) . 

(4)  To  2  gm.  of  chloral  hydrate  in  a  dry  test-tube 
add  5  c.c.  of  C.P.  H^SO*,  and  warm  gently  while 
shaking.     An  oily  liquid   (chloral)   separates  as  a 
top  layer.     Cool  the  tube  to  room  temperature, 
and  add  5  c.c.  of  chloroform  which  is  free  of  alcohol 
and  water.     Draw  off  the  top  layer  with  a  dry 
pipette,   and   allow   the   chloroform   to   evaporate; 
the  residue  in  the  dish  will  take  up  moisture  from 


156  ORGANIC  CHEMISTRY 

the  air,  until  finally  chloral  hydrate  crystals  are 
formed. 

Chloral  Substitutes.  Many  derivatives  of  chloral 
have  been  synthetized  with  the  object  of  correcting 
the  tendency  which  chloral  hydrate  has  to  depress 
the  circulation.  Such  are: 

Butyl-chloral  hydrate  (croton  chloral), 

CH3  •  CHC1  -  CC12  •  CH(OH)  2. 
Chloralformamide,  (chloralamide) , 

/OH 
CCl3-CH<NHOCH< 

is  a  combination  of  chloral  hydrate  with  formamide. 
HCONH2. 

Chloralose  (chloral  +  glucose),  CgHnClsOe. 

Hypnal  (chloral  +  antipyrin) . 

Dormiol  (chloral  condensed  with  amylene  hydrate) 

Isopral,  trichlorisopropylalcohol, 

'OH 
CH3* 


CHAPTER  XII 

FATTY  ACIDS   AND   ETHEREAL   SALTS.    FURTHER 
OBSERVATIONS  IN  PHYSICAL  CHEMISTRY 

ACIDS 

ACIDS  are  defined  as  substances  which,  when 
dissolved  in  water,  dissociate  in  such  a  way  as  to 
furnish  hydrogen  ions  (see  p.  67).  Most  organic 
acids  dissociate  but  feebly;  they  are  therefore 
weak  acids  as  compared  with  inorganic  acids  (see 
p.  173).  The  majority  of  organic  acids  contain 
the  carboxyl  group. 

A  general  method  of  production  of  carboxylic 
acids  is  by  hydrolysis  1  of  a  cyanide  (see  experi- 
ment under  acetic  acid) : 

HCN+2H2O=H-COONH4, 

(Ammonium  formate) 

CH3CN  +2H20  =  CH3  •  COONH4.     ) 

(Ammonium  acetate) 

The  acids  to  be  studied  at  this  point  are  called 
fatty  acids,  because  common  fats  contain  some 
members  of  this  series  of  acids  (in  combination  with 
glycerol).  They  are  monobasic,  i.e.,  they  contain 
only  one  displaceable  hydrogen  atom  in  the  acid 
group.  They  conform  to  the  general  formula, 

1  Hydrolysis  means  introducing  H20  into  the  molecule  of 
the  substance  to  be  hydrolyzed,  the  result  being  a  product  quite 
different  from  the  original  substance. 

157 


158  ORGANIC  CHEMISTRY 

CnH2ri02.  They  are  the  end  products  of  the  oxi- 
dation of  primary  alcohols,  of  the  methyl  alcohol 
series,  since  they  can  be  obtained  by  oxidation  of 
aldehydes : 

H.CHO+O=H-COOH. 

The  OH  of  carboxyl  can  be  proved  to  be  hydroxyl 
by  the  reaction  with  PC13  (see  pp.  136  and  146), 
thus: 

3CH3  •  COOH  +PC13  =  3CH3  •  COC1 +H3P03. 

It  would  be  desirable  to  call  this  series  of  acids 
the  formic  acid  series,  since  the  term  fatty  is  mis- 
leading. 

The  boiling-points  of  these  acids  increase  steadily 
with  increase  in  the  number  of  carbon  atoms.  For 
some  unexplained  reason  a  similar  statement  is  not 
true  of  the  melting-points,  but  on  the  contrary  the 
acids  having  an  odd  number  of  carbon  atoms  have 
each  a  lower  melting-point  than  the  next  acid  having 
one  less  carbon  atom. 

Formic  acid  (methanoic  acid),  H-COOH,  is  a 
liquid. 

(1)  It  can  be  made  by  oxidation  of  formaldehyde 
by  hydrogen  peroxide  in  alkaline  solution: 

H  •  CHO  +H2O2  +KOH  =  H  •  COOK  -f  2H20. 

The  acid  can  then  be  liberated  from  the  potassium 
formate. 

(2)  Moist  CO  is  absorbed  by  soda-lime  at  190°- 
220°,  forming  sodium  formate: 

CO+NaOH=H-COONa. 


FATTY  ACIDS  AND  ETHEREAL  SALTS         159 

(3)  Moist  C02  coming  in  contact  with  metallic 
potassium  forms  potassium  formate  and  potassium 
bicarbonate : 

2K  +2C02  +H2O  =  HCOOK  +KHCO3. 

(4)  Oxalic  acid  when  heated  with  glycerol  (gly- 
cerine) decomposes  to  formic  acid  and  carbon  dioxide 
(see  exp.). 

Formic  acid  occurs  in  red  ants,  and  in  stinging 
nettles.  It  is  very  irritant,  causing  blisters  when 
applied  to  the  skin.  Formic  acid  boils  at  101°; 
it  solidifies  at  a  low  temperature,  and  melts  at 
8.3°.  Its  specific  gravity  is  1.2187  at  20°.  It  is  a 
strong  reducing  agent,  reducing  silver  and  mercury 
compounds  to  the  metal  (see  exp.).  The  full 
structural  formula,  H — C=0,  shows  that  it  con- 

0— H 

tains  the  aldehyde  group  overlapping  the  acid  group, 
carbonyl  being  common  to  both.  It  oxidizes  to 
carbon  dioxide  and  water.  It  is  a  stronger  acid 
than  acetic  acid.  When  treated  with  concentrated 
sulphuric  acid  it  is  decomposed,  with  evolution  of 
carbon  monoxide  (see  exp.  3). 

EXPERIMENTS.  (1)  Prepare  formic  acid  as  fol- 
lows: Into  a  half-liter  flask  put  50  c.c.  of  an- 
hydrous glycerol  (which  has  been  heated  at  170° 
for  an  hour);  add  50  gm.  of  crystallized  oxalic 
acid.  Suspend  a  thermometer  in  the  cork,  so  that 
its  bulb  is  in  the  liquid.  Heat  gradually  on  a  sand- 
bath.  Connect  with  a  condenser.  Carbon  dioxide 


160  ORGANIC  CHEMISTRY 

is  evolved,  and  formic  acid  begins  to  distill  at  about 
115°  (temperature  of  the  liquid).  When  the  tem- 
perature reaches  150°,  cool  the  mixture  to  about 
50°,  then  add  50  gm.  of  oxalic  acid.  Heat  again  up 
to  150°.  If  the  mixture  is  overheated,  acrolein 
(p.  302)  will  be  produced,  which  is  a  very  disagree- 
able gas.  Test  some  of  the  acid  distillate  for  formic 
acid  as  below.  If  less  than  200  c.c.  of  distillate  is 
obtained,  dilute  it.  In  the  meantime  copper  hydrox- 
ide has  been  prepared  by  treating  CuS04  solution 
with  KOH  until  slightly  alkaline,  diluting  and 
filtering.  In  similar  manner,  prepare  lead  hydroxide 
from  lead  nitrate  solution.  Add  to  half  of  the  formic 
acid  copper  hydroxide,  warming  the  mixture.  When 
copper  hydroxide  no  longer  dissolves,  filter  and  set 
away  for  slow  evaporation.  To  the  rest  of  the  acid 
add  lead  hydroxide  and  proceed  as  with  the  copper 
formate. 


(Glycerol)  (Oxalic  acid) 

=  C3H6(OH)2pCHO  +H20  +C02 

(Monoformin  or 
glyceryl  monoformate) 

C3H5(OH)2OCHO  +H20  =  H  -  COOH  +C3H5(OH)3. 

(Formic  acid)  (Glycerol) 

(2)  Test  for  formic  acid  in  the  distillate  as  fol- 
lows:   Warm  a  few  c.c.  to  50°,  add  HgO,  and  shake 
vigorously.     Filter  and  boil  the  filtrate  one  minute 
a  gray  precipitate  of  mercury  develops: 

HgO  +H-  COOH  =Hg+C02+H20. 

(3)  Into  a  test-tube  put  3  c.c.  of  undiluted  formic 
acid;    add  slowly  6  c.c.  of  H2SO4.     Cork  quickly 


FATTY  ACIDS  AND  ETHEREAL  SALTS         161 

with  a  cork  through  which  passes  a  bent  delivery- 
tube  the  end  of  which  is  to  dip  into  a  few  cubic 
centimeters  of  dilute  haemoglobin  solution  in  another 
test-tube.  The  haemoglobin  is  changed  to  carbon- 
monoxide-haemoglobin,  which  has  a  cherry-red  tint. 
The  haemoglobin  solution  is  made  by  adding  a  drop 
of  blood  to  a  little  distilled  water. 

Acetic  acid,  CHsCOOH.  There  are  various  ways 
by  which  ethyl  alcohol  may  be  oxidized  to  yield 
acetic  acid.  In  the  laboratory,  the  addition  of 
spongy  platinum  to  alcohol  contained  in  an  open 
vessel  causes  the  atmospheric  oxygen  to  attack  the 
alcohol,  oxidizing  it  and  producing  acetic  acid.  The 
spongy  platinum  itself  undergoes  no  change;  it  is 
a  catalytic  agent,  merely  transferring  the  oxygen  to 
the  alcohol. 

Pure  alcohol  or  alcohol  diluted  with  pure  water 
does  not  spontaneously  become  converted  into  acetic 
acid  when  exposed  to  the  air,  but  does  so  if  the 
dilute  alcoholic  solution  contains  nitrogenous  matter. 
This  is  because  of  the  growth  in  the  latter  solution 
of  a  microorganism  derived  from  the  air  (Mycoderma 
aceti),  which,  like  spongy  platinum,  transfers  atmos- 
pheric oxygen  to  the  alcohol.  Nitrogenous  matter 
is  necessary  for  the  life  of  this  organism.  It  is  in 
this  way  that  wine  becomes  converted  into  vinegar. 
Mere  exposure  of  wine  or  cider  to  air  would,  how- 
ever, occupy  too  much  time  to  produce  sufficient 
vinegar  to  meet  the  demands  of  commerce,  and 
consequently  the  above  process  has  to  be  accelerated. 
This  is  done  by  allowing  the  wine  to  percolate  slowly 


162  ORGANIC  CHEMISTRY 

through  freely  perforated  barrels  filled  with  beech 
shavings  previously  sown  with  the  mycoderma 
by  soaking  them  in  strong  vinegar.  A  slight 
amount  of  heat  is  generated  during  the  oxidation; 
this  creates  currents  of  air,  which  enter  the  barrels 
through  the  perforations  in  their  sides,  and  in  this 
way  a  sufficiency  of  oxygen  for  the  process  is  sup- 
plied. Other  alcoholic  solutions  besides  wine  may 
be  used  for  the  purpose,  e.g.,  cider  or  beer,  and 
frequently  some  alcohol  obtained  by  fermenting 
glucose  is  added  to  these.  The  amount  of  alcohol 
in  such  solutions  should  not,  however,  be  over  10%. 
The  resulting  vinegars  contain  about  5%  of  acetic 
acid,  besides  various  aromatic  bodies. 

To  obtain  acetic  acid  in  a  pure  state,  fermentation 
of  alcoholic  liquids  is,  however,  not  employed.  For 
this  purpose  hard  wood  is  subjected  to  what  is 
known  as  destructive  distillation.  It  is  heated  at 
low  temperature  (200°)  in  an  iron  retort  from  which 
air  is  excluded,  and  the  vapors  condensed.  The 
resulting  distillate  consists  of  a  mixture  of  a  tarry 
material  and  a  watery  liquid  known  as  pyroligneous 
acid.  This  latter  contains,  besides  acetic  acid 
(4-10%),  various  other  organic  substances,  par- 
ticularly acetone  (0.5%)  and  methyl  alcohol  (1-2%). 
By  fractional  distillation  several  of  these  are  sepa- 
rated, the  second  fraction,  which  contains  most  of 
the  acetic  acid,  being  neutralized  with  quicklime 
and  evaporated;  the  resulting  calcium  acetate  is 
then  freed  of  impurities  by  heating  and  treated  with 
hydrochloric  acid  so  as  to  liberate  the  acetic  acid, 
which  is  then  distilled.  This  first  distillate  contains 


FATTY  ACIDS  AND  ETHEREAL  SALTS         163 

about  36  to  50%  of  acetic  acid.  To  purify  it  further, 
this  dilute  acid  is  passed  through  charcoal,  and  then 
redistilled  over  potassium  dichromate.  The  final 
distillate,  however,  still  contains  water.  To  re- 
move this,  the  solution  is  cooled  down  to  a  low 
temperature,  when  most  of  the  acid  solidifies  and 
the  water  can  be  drained  off.  Since  pure  acetic 
acid  solidifies  on  cooling,  it  is  often  called  glacial 
acetic  acid;  this  should  not  contain  over  1%  of  water. 
Acetic  acid  is  a  colorless  liquid,  boiling  at  118.1° 
(corrected)  and  with  a  specific  gravity  of  1.055  at  15°. 
By  dilution  with  water  the  specific  gravity  rises, 
attaining  the  maximum  when  an  acid  of  80%  is 
obtained  (see  table  in  Appendix,  p.  450).  When 
glacial  acetic  acid  is  cooled  it  solidifies,  the  crystals 
again  melting  at  16.6°.  It  has  a  characteristic 
odor  and,  in  dilute  solution,  a  pleasant  acid  taste. 

EXPERIMENTS.  (1)  Into  a  small  fractionating 
flask  put  6  gm.  of  powdered  potassium  dichromate 
and  10  c.c.  of  concentrated  H^SO*;  connect  with  a 
condenser;  then,  by  means  of  a  dropping  funnel 
suspended  by  the  cork  of  the  flask,  add  drop  by  drop 
12  c.c.  of  20%  alcohol.  Heat  until  enough  dis- 
tillate is  secured  for  the  following  tests. 

(2)  Acetic  acid  tests,  (a)  To  5  c.c.  of  the  solution 
add  1  c.c.  of  H2S04  and  a  few  drops  of  alcohol. 
Shake,  and  note  the  odor  of  ethyl  acetate  on  warm- 
ing. 

(6)  Neutralize  5  c.c.  with  sodium  carbonate  solu- 
tion. When  neutral  add  a  few  drops  of  ferric 
chloride  solution.  The  mixture  becomes  brownish 


164  ORGANIC  CHEMISTRY 

red;  on  boiling  a  colored  precipitate  separates  out. 
Filter;  the  filtrate  is  colorless. 

(3)  Cool  some  glacial  acetic  acid  in  a  large  test- 
tube  by  means  of  ice-water,  stirring  with  a  ther- 
mometer. Melt  the  crystals  with  the  heat  of  the 
hand,  keeping  the  thermometer  in  motion.  Note 
the  temperature  at  which  the  acid  melts. 

In  all  its  reactions  acetic  acid  conforms  with  the 
structural  formula  CH3COOH.  Since,  in  our  prac- 
tical exercises,  we  shall  perform  nearly  all  the  reac- 
tions that  have  enabled  chemists  to  ascribe  this 
formula  to  acetic  acid,  it  may  be  advantageous,  when 
describing  these  reactions,  to  indicate  how  they  bear 
out  the  structural  formula.  To  illustrate  clearly  just 
exactly  how  a  structural  formula  is  arrived  at  by  the 
chemist,  let  us  suppose  that  we  are  working  with  an 
unknown  substance  which,  by  elementary  analysis 
and  molecular  weight  determination  (see  Chapter 
III  and  p.  40),  we  have  found  to  possess  the  em- 
pirical formula  C2H402. 

For  the  sake  of  clearness  of  comprehension  of  the 
steps  of  the  argument  for  the  structural  formula, 
a  tabulated  statement  will  be  given  before  the  de- 
tailed discussion. 

(1)  C2H302 — H,  proof:  monobasic  acid. 

(2)  C2H30 — OH,  proof:  phosphorus  chloride  reac- 
tion. 

(3)  CH3— (OC)— OH,  methyl   group  proved,  by 
production  of  CEU  from  an  acetate. 

(4)  CH3— COO— H,  proof:    the  addition  of  C02 
to  CH3Na  forming  an  acetate. 


FATTY  ACIDS  AND  ETHEREAL  SALTS         165 

(5)  Synthetically  by  the  building  up  of  methyl 
cyanide  from  CH4,  and  the  hydrolysis  of  the  cyanide 
to  acetic  acid. 

(1)  In  testing  the  reaction  of  this  substance  we 
shall  have  found  it  acid,  and  on  neutralizing  it 
with  monacid  bases  and  evaporating,  crystalline 
salts  will  be  obtained,  which  on  analysis  will  be 
found  to  contain  one  H  atom  less  than  the  acid 
itself.  These  facts  indicate  that  the  acid  dis- 
sociates into  a  cation  of  hydrogen,  H',  and  an  anion 
represented  by  the  remainder  of  the  molecule, 
C2H30/2.  In  other  words,  one  of  the  four  H  atoms 
must  be  represented  in  the  structural  formula  as 
different  from  the  others:  C2H3O2 — H. 

The  hydroxides  that  may  be  employed  to  neu- 
tralize the  acid  are  conveniently  divided  into  metallic 
and  organic. 

Metallic  salts  of  acetic  acid — the  acetates — are 
very  numerous.  Sodium  and  potassium  acetates 
(C2H302K;  C2H302Na)  are  extensively  used  for 
various  purposes  in  the  laboratory.  Lead  acetate, 
Pb(C2H3O2)2,  on  account  of  its  possessing  a  peculiar 
sweetish  taste,  is  known  as  sugar  of  lead.  It  is 
used  in  medicine  as  an  astringent.  When  it  is  mixed 
with  lead  oxide  the  compound  is  known  as  basic 
lead  acetate.  In  the  presence  of  carbonic  acid, 
basic  lead  acetate  forms  densely  opalescent  solu- 
tions on  account  of  the  insoluble  lead  carbonate 
that  is  formed.  In  boiled  distilled  water  the  solu- 
tions are  nearly  clear.  The  lead  acetates  are  valu- 
able precipitating  reagents  and  are  extensively 


166  ORGANIC  CHEMISTRY 

employed  for  this  purpose  in  biochemistry.  Copper 
acetate  is  a  well-known  salt  and  is  used  as  a  reagent. 
All  these  acetates  are  most  simply  prepared  by  dis- 
solving the  metallic  hydroxides  in  acetic  acid. 

Ethereal  Salts  of  Acetic  Acid.  In  studying  alcohol 
we  saw  that  its  hydroxyl  group  (OH)  is  replaceable, 
for  example,  by  halogens  (Cl,  Br,  or  I),  or,  as  in  the 
case  of  ethereal  salts,  by  the  organic  acid  radicle 
C2H3O2.  Since  the  ethereal  salts  are  of  consider- 
able importance  and  are  numerous,  we  shall  post- 
pone their  consideration  till  later. 

(2)  So  far  we  have  seen  that  one  of  the  H  atoms 
in  acetic  acid  differs  considerably  from  the  others. 
By  another  set  of  reactions  we  can  show  that  this 
same  H  atom  must  be  intimately  connected  with  one 
of  the  O  atoms,  the  resulting  group,  which  we  have 
already  me't  with  in  alcohols,  being  hydroxyl.  This 
hydroxyl  is,  as  we  have  seen,  replaceable  by  halo- 
gens. Thus,  when  acetic  acid  is  treated  with  PC13, 
the  following  reaction  ensues:  3C2H302H+PC13 
=  3C2H3OC1+H3P03.  The  hydroxyl  group  is  evi- 
dently substituted  by  Cl,  just  as  in  the  case  of  water 
or  alcohol: 

3HOH+PC13  =  3HC1+P(OH)3. 

We  must  therefore  assume  that  acetic  acid  can 
under  certain  conditions  be  caused  to  split  up  into 
C2H30  and  OH.  The  former  of  these  is  called  the 
acetyl  group.  An  acid  radical  of  this  kind  is  called 
an  acyl. 

Acetyl  chloride,  C2H3OC1,  belongs  to  the  class  of 
acid  chlorides  (or  acyl  halogenides)  and  may  be  pre- 


FATTY  ACIDS  AND  ETHEREAL  SALTS 


167 


pared  by  the  method  described  in  the  following 
experiment : 

EXPERIMENT.  Put  25  c.c.  of  glacial  acetic  acid 
into  a  fractionating  flask.  Suspend  a  dropping 
funnel  by  the  cork.  Attach  the  flask  to  a  con- 


FIG,  21. 

denser.  As  a  receiver,  fit  a  filtering  flask  to  the 
condenser-tube  with  a  cork  (see  Fig.  21),  and  attach 
to  the  side  tube  of  the  filtering  flask  a  calcium 
chloride  tube.  All  moisture  must  be  carefully 
excluded  in  this  manner.  Add  to  the  acid  through 
the  dropping  funnel  20  gm.  of  phosphorus  trichloride, 
the  flask  being  immersed  in  a  bath  of  ice-water. 


168  ORGANIC  CHEMISTRY 

When  it  has  cooled,  substitute  a  warm  bath  at  40°- 
50°.  Keep  the  temperature  at  this  point  until 
the  evolution  of  HC1  ceases  (having  the  apparatus 
under  a  hood).  Bring  the  water  of  the  bath  to 
active  boiling  and  distill  the  acetyl  chloride. 

It  is  a  colorless  volatile  fluid,  boiling  at  51°.  In 
the  presence  of  water  it  readily  decomposes,  as  re- 
presented in  the  following  equation: 


C2H3OJC1 +HjOH  =  C2H3OOH  +HC1. 

The  atmospheric  moisture  is  sufficient  to  cause  this 
reaction,  so  that  when  acetyl  chloride  is  exposed  to 
the  air  it  ^umes,  the  fumes  being  very  suffocating  and 
disagreeable.  (It  should  be  kept  in  tightly  stoppered 
bottles.)  The  H  of  the  hydroxyl  group  of  alcohols 
reacts  similarly  with  acetyl  chloride,  thus: 

C2H3o|a4^ioC2H5  =  C2H3OOC2H5+HC1, 

.  (Ethyl  acetate) 

the  ethereal  salt  of  acetic  acid  with  the  radicle  of 
the  alcohol  used  being  formed.  On  this  account 
acetyl  chloride  is  an  invaluable  reagent  for  the 
detection  of  alcoholic  hydroxyl;  if  we  find  that  a 
substance  when  treated  with  acetyl  chloride  forms 
an  ethereal  acetate,  we  may  conclude  that  the  sub- 
stance contains  hydroxyl  other  than  the  hydroxyl 
of  carboxyl. 

EXPERIMENT.  To  3  c.c.  of  absolute  alcohol  add 
slowly  3  c.c.  of  acetyl  chloride.  HC1  is  evolved. 
Cool  the  mixture  and  neutralize  with  NaOH.  Note 
the  odor  of  ethyl  acetate. 


FATTY  ACIDS  AND  ETHEREAL  SALTS          169 

The  above  experiments,  therefore,  justify  our  writing 
the  formula  C2H30 — OH.  Further  corroboration 
of  this  is  found  in  the  fact  that  two  molecules  of 
acetic  acid  can  be  made  to  unite  with  the  loss  of  a 
molecule  of  water,  thus:' 

C2H300|H     c2H8Ov 

H    |=  >0+H20, 

CaH80/ 


the  resulting  body  being  acetic  anhydride.  For 
practical  purposes  acetic  anhydride  may  be  prepared 
by  acting  on  acetyl  chloride  with  anhydrous  sodium 
acetate,  thus: 

C2H3OOiNa! 

+NaCl. 


C2H30 


Cll     C2H3 


It  is  a  fluid  giving  off  a  suffocating  vapor.  Added 
to  water,  it  sinks  to  the  bottom  of  the  vessel,  but 
gradually  becomes  reconverted  into  acetic  acid.  Its 
readiness  to  re-form  acetic  acid  causes  it  to  attack 
the  hydroxyl  group  of  alcohols  and  other  hydroxyl 
compounds,  one  of  the  acetyl  groups  becoming 
thereby  attached  in  place  of  the  OH  group,  thus: 


C2H5|OH  OC3EJ  =  C2H5OOC2H3+C2H3OOH. 

JL~QX^  (Ethyl  acetate)  (Acetic  acid) 

\)C2H3 

Like  acetyl  chloride,  it  may  therefore  be  em- 
ployed for  ascertaining  whether  a  substance  con- 
tains hydroxyl  not  in  carboxyl,  and  if  so,  how  many 
such  groups  it  contains  (see  p.  206). 


170  ORGANIC  CHEMISTRY 

(3)  There  remains  for  us  to  find  out  how  the  acetyl 
radicle  C2H3O  is  composed.     A  clue  to  this  is  fur- 
nished by  the  observation  that  methane,  CBU,  and 
a   carbonate   are   obtained   by  heating  anhydrous 
sodium  acetate  with  soda-lime  (see  exp.,  p.  120): 

C2H3OONa+NaOH  =Na2C03+CH4. 

This  must  mean  that  the  two  carbon  atoms  are  of 
different  value  and  that  one  of  them  exists  in  com- 
bination with  hydrogen  as  methyl,  CH3. 

Further  corroboration  of  this  is  furnished  also  by 
the  fact  that  the  three  H  atoms  which  belong  to  the 
methyl  group  can  be  separately  replaced  by  chlorine 
atoms,  thus  forming  the  substitution  products 
mono-,  di-,  or  tri-chloracetic  acid: 

C2H30  -  OH + C12  =  C2H2C10  -  OH  +HC1, 
C2H2C10  •  OH +C12  =  C2HC120  •  OH  +HC1, 
C2HC120  •  OH  +C12  =  C2C130  •  OH +HC1. 

The  resulting  substitution  products  retain  the  acid 
properties  of  acetic  acid,  such  as  the  power  of  form- 
ing ethereal  salts,  anhydrides,  etc.  The  chlor- 
acetic  acids  are  much  stronger  than  acetic  acid,  and 
the  acid  power  increases  with  the  number  of  chlorine 
atoms. 

(4)  If  we  represent  acetic  acid  as  containing  a 
methyl     group,     its     formula     must     be    written 
CCH3OOH,  COCH3OH,  or  CH3COOH:    which  of 
these  is  correct?    The  valence  of  carbon  prevents 
C  of  CH3  from  having  more  than  one  linking  to  the 
rest  of  the  molecule;  and  for  the  other  C  to  satisfy 


FATTY  ACIDS  AND  ETHEREAL  SALTS         171 

its  valence,  it  is  necessary  that  it  be  linked  to  both 
oxygen  atoms  as  well  as  to  C  of  CH3;  therefore  the 
structure  must  be  CH3COOH.  Further  evidence 
that  the  group  COOH  does  actually  exist  in  acetic 
acid  is  given  by  the  following  observations: 

(a)  The  formation  of  sodium  acetate  by  treating 
sodium  methyl  with  CO2 : 

CH3Na+C02  =CH3COONa. 

(6)  The  result  of  electrolysis  of  acetic  acid.  The 
cation  H'  is  liberated  at  the  cathode;  the  anion 
CH3COO'  passes  to  the  anode,  where  it  is  liberated 
as  CO2  and  ethane  (the  two  methyl  (CHs)  groups 
from  two  molecules  having  united). 

(5)  By  synthesis,  as  shown  by  the  equations: 

CH4  +Br2  =  CH3Br +HBr. 
CH3Br  +KCN  =  CH3CN  +KBr. 
CH3CN+2H20=CH3COOH+NH3  (p.  256). 

EXPERIMENT.  Take  2  gm.  of  acetonitrile  (pre- 
pared as  directed  in  the  experiment  under  methyl 
cyanide,  on  p.  255)  and  mix  with  10  c.c.  of  60% 
KOH  in  a  small  flask.  Attach  the  flask  to  an 
upright  (reflux)  condenser.  Heat  for  forty-five 
minutes.  Note  the  ammonia  escaping  from  the 
top  of  the  condenser.  Neutralize  the  resulting  fluid 
with  HC1  and  test  for  acetic  acid  (see  previous 
experiments) : 

CH3CN  +2H20  =  CH3  -  COONH4, 
CH3  •  COONH4  +KOH  =  CH3  •  COOK +NH3  +H2O 


172  ORGANIC  CHEMISTRY 

THE  CAUSE  OF  THE  RELATIVE  STRENGTHS  OF  ACIDS 
(AND  BASES) 

It  is  important  to  understand  what  it  is  that  con- 
stitutes the  strength  of  an  acid  or  alkali.  This 
obviously  cannot  be  gauged  by  titration  with 
indicators:  a  normal  solution  of  any  acid  will  be 
neutralized  by  an  equal  volume  of  a  normal  solution 
of  any  alkali,  and  yet  such  acids  as  HC1,  H2S04, 
etc.,  are  far  more  reactive — are  stronger,  in  other 
words — than  such  acids  as  acetic,  lactic,  etc.  This 
difference  in  strength  is  explained  by  the  fact  that 
only  a  certain  fraction  of  any  acid  or  alkali  is  effect- 
ive, the  value  of  this  fraction  being  proportional 
to  the  strength  of  the  acid  or  alkali.  The  effective 
fraction  of  an  acid  is  that  portion  of  it  which  becomes 
ionized.  In  solution,  acids  ionize  into  a  cation  of 
hydrogen  or  hydrion  (which  being  charged  with  + 
electricity  is  often  called  the  positive  ion)  and 
an  anion  of  the  rest  of  the  molecule  (see  p.  66). 
In  the  case  of  solutions  of  strong  acids  a  much 
greater  proportion  of  acid  ionizes  in  this  way  than 
in  the  case  of  an  equimolecular  solution  of  weak 
acids.  We  may  therefore  state  that  the  active 
acidity  of  a  solution  of  an  acid  depends  on  the  concen- 
tration of  the  hydrogen  ions. 

In  the  case  of  bases,  e.g.,  KOH  and  NEUOH, 
dissociation  in  solution  into  cations  of  the  metal  or 
its  equivalent  (K,NBU)  and  into  anions  of  hydroxyl 
occurs.  It  is  the  concentration  of  the  hydroxyl  ions 
(hydroxions)  which  determines  their  strength  (cf. 
Amines,  p.  260). 


FATTY  ACIDS  AND  ETHEREAL  SALTS         173 

In  a  solution  of  HC1,  for  example,  there  exist: 
(a)  undissociated  HC1,  (6)  cations  of  H',  and  (c) 
anions  of  Cl'.  A  solution  of  acetic  acid  contains 
(a)  undissociated  CH3-COOH,  (6)  cations  of  IT, 
and  (c)  anions  of  CHsCOO'.  The  amount  of  (a)  in 
the  two  cases  will  be  very  different,  there  being  much 
less  dissociation  in  the  case  of  acetic  acid  than  in 
the  case  of  hydrochloric  acid.  In  every  acid, 
therefore,  there  must  exist  a  certain  proportion  be- 
tween the  undissociated  and  the  dissociated  por- 
tions. This  will,  of  course,  vary  at  different  dilu- 
tions, for  it  will  be  remembered  that  dissociation 
increases  with  dilution  (see  p.  68).  Since  it  is 
known  that  the  electrical  conductivity  of  a  solu- 
tion depends  on  the  amount  of  dissociation  of  the 
electrolyte  dissolved  in  it,  we  may  obtain  a  value 
for  this  proportion  by  measurement  of  electrical 
conductivity.  In  decinormal  HC1  solution  91% 
of  the  molecules  are  ionized,  as  compared  with 
1.3%  in  decinormal  acetic  acid.  In  decinormal 
NaOH  solution  84%  of  the  molecules  are  ionized, 
but  only  1.4%  in  decinormal  NBUOH.  (Consult 
the  tables,  p.  451). 

ETHEREAL  SALTS.    ESTERS. 

Corresponding  to  the  salts  of  inorganic  chemistry 
there  are  derivatives  of  organic  acids  in  which  the 
hydrogen  of  carboxyl  is  replaced  by  some  hydro- 
carbon radicle.  Thus  ethyl  acetate  has  the  formula 
CH3COO-C2ll5,  from  which  it  is  seen  that  the  two 
constituent  radicles  are  linked  together  through  an 
oxygen  atom  as  in  the  ethers  (see  p.  132).  On  this 


174  ORGANIC  CHEMISTRY 

account  such  compounds  are  usually  called  ethereal 
salts,  or  more  briefly  esters.  In  a  looser  sense,  com- 
pounds of  mineral  acids  with  organic  radicles,  as  ethyl 
nitrate,  C2H5ONO2,  and  ethyl  sulphate,  (C2H5)2S04, 
are  included  in  this  group;  but  since  such  as  these 
have  been  considered  elsewhere,  we  shall  study  at 
present  only  those  salts  in  which  organic  acids  are 
in  combination. 

Inorganic  salts  are  immediately  formed  when  solu- 
tions of  an  acid  and  a  base  are  mixed,  for,  both  of 
these  being  ionized,  the  hydrogen  ion  of  the  acid 
immediately  unites  with  the  hydroxyl  ion  of  the 
base  to  form  water  : 

(B-  +OH')  +(H-  +Z')  =  (B-  +Z')  +H2CM 

(Base)  (Acid)  (Salt) 

Esters  are,  however,  not  thus  readily  formed,  for 
the  reacting  hydroxide,  being  an  alcohol,  is  not 
ionized,  but  remains  as  a  molecule,  and  on  this  the 
acid  only  slowly  acts: 

R  -  OH  +  (H-  +Z')  =  R  •  Z  +H20. 

(Alcohol)  (Acid)  (Ester) 

Inorganic  are  distinguished  from  ethereal  salts 
not  only  in  their  ease  of  formation  but  also  in  their 
dissociability  in  solution,  the  former  being  usually 
entirely  dissociated  in  solution,  the  latter  not  at  all 
so.  In  this  connection  it  is  of  great  importance  to 
point  out  that  salts  of  organic  acids  with  metals 
do  undergo  dissociation  in  solution,  and  to  about 


equation  will  serve  as  an  example  of  how  ions  are 
represented  in  a  reaction. 


FATTY  ACIDS  AND  ETHEREAL  SALTS         175 

the  same  extent  as  inorganic  salts.  Thus  in  a 
solution  of  ethyl  acetate  there  are  no  free  ions, 
whereas  in  one  of  sodium  acetate  dissociation  into 
Na*  and  CH3COO'  ions  occurs. 

Mass  Action.  One  of  the  notable  illustrations  of 
mass  action  is  ester  formation.  The  formation  of 
an  ethereal  salt  when  an  alcohol  and  an  acid  are 
directly  mixed,  although  slow,  yet  proceeds  until 
a  balance  between  the  four  constituents  is  established 
(i.e.,  between  acid,  alcohol,  salt,  and  water).  This 
is  because  the  reaction  is  a  reversible  one;  in  other 
words,  whenever  a  slight  excess  of  water  comes  to 
exist  in  the  mixture,  it  decomposes  the  ester  into  the 
acid  and  alcohol,  thus: 

CH3COOC2H5+HOH  ?±  CH3COOH+C2H5OH. 

Such  reversible  reactions  are  often  represented  in 
equations  by  two  arrows  in  place  of  the  sign  of 
equality. 

The  mixture  comes  to  a  point  of  equilibrium 
when  0.669  part  of  a  gram  molecule  of  ester  is  pres- 
ent, provided  we  started  with  one  gram-molecule 
of  both  acid  and  alcohol.  At  the  beginning  of  the 
reaction  the  mass  action  of  both  alcohol  and  acid 
is  most  marked,  forcing  ester  production,  the  re- 
verse action  being  very  slight.  As  ester  and  water 
accumulate,  ester  formation  slows  up  and  the 
reverse  action  begins  to  figure  in  the  reaction, 
until  finally  the  mass  action  of  the  water  to  cause 
hydrolysis  is  as  pronounced  as  that  of  the  alcohol 
and  acid  to  cause  esterification.  The  equilibrium 
is  not  really  static;  for  the  action  and  the  reverse 


176  ORGANIC  CHEMISTRY 

action  are  going  on  constantly  to  an  equal  degree, 
thus  maintaining  a  balance. 

If  a  gram-molecule  of  both  the  ester  and  water 
are  mixed,  hydrolysis  occurs,  but  apparently  ceases 
when  the  same  equilibrium  point  as  for  esterifica- 
tion  is  reached.  In  this  case  also  the  equilibrium 
mixture  contains  about  two-thirds  of  a  gram-mole- 
cule of  ester  and  water,  and  one-third  of  a  gram- 
molecule  of  alcohol  and  acid. 

The  amount  of  ester  thus  formed  depends  on  the 
relative  amounts  of  acid  and  alcohol  present  and  not 
on  the  temperature.  With  a  given  amount  of  alco- 
hol an  increase  in  the  amount  of  acid  increases  the 
yield  of  ethereal  salt,  and,  conversely,  the  same 
is  true  with  a  given  amount  of  acid  when  more 
alcohol  is  used.  Since  the  progress  of  the  formation 
of  the  above  ester  can  be  followed  by  titrating  the 
residual  acid,  the  reaction  has  been  extensively 
employed  in  studying  the  laws  of  mass  action. 

The  fundamental  law  of  mass  action  states  that 
the  product  of  the  number  of  gram-molecules  per 
liter  of  the  substances  on  the  one  side  of  the  equa- 
tion, divided  by  the  product  of  these  on  the  other 
side,  is  equal  to  some  constant.  In  the  case  of  the 
above  reaction  we  have  therefore  the  equation: 

C  acidxC  alcohol 
-=—     — ^—      —  =  constant, 
C  ester  xC  water 

where  C  represents  gram-molecules  per  liter  of  the 
reacting  substances. 

It  will  be  evident  that  if  we  increase  C  acid  while 
C  alcohol  remains  constant,  then  C  ester  must 


FATTY  ACIDS  AND  ETHEREAL  SALTS         177 

increase,  which  leads  us  to  the  conclusion  that  if 
enough  acid  is  added,  all  the  alcohol  will  become 
converted  into  ester,  or,  conversely,  that  if  more 
alcohol  is  added,  the  acid  remaining  constant,  the 
same  will  be  true.  For  example  if  one  gram- 
molecule  of  acetic  acid  and  eight  gram-molecules 
of  ethyl  alcohol  interact,  they  come  to  equilibrium 
when  96.6%  of  a  gram-molecule  of  ethyl  acetate  is 
formed. 

Temperature  does  not  affect  the  constant  to  any 
marked  degree,  so  that  it  does  not  influence  the 
ultimate  amount  of  ethereal  salt  produced.  On 
the  other  hand,  it  greatly  influences  the  rate  of 
reaction,  i.e.,  the  time  that  it  takes  before  the 
condition  of  chemical  equilibrium  is  reached.  Thus 
a  rise  in  temperature  increases  the  velocity  of  the 
reaction  (as  a  rule  the  rate  doubles  for  each  increase 
of  ten  degrees  in  temperature).  At  55°  cane  sugar 
is  hydrolyzed  by  acids  about  five  times  as  fast  as 
at  25°.  By  studying  different  alcohols  and  acids, 
it  has  been  found  that  if  equimolecular  amounts 
of  acid  and  alcohol  be  used,  the  limit  of  esterification 
varies  only  slightly;1  but  the  rate  is  much  greater 
for  such  acids  as  acetic  than  it  is  for  such  as  ben- 
zoic,  and  for  primary  than  for  secondary  alcohols. 

The  amount  of  ester  produced  can  be  greatly 

1  For  example  the  per  cent  of  a  gram-molecule  of  ester  formed 
by  some  alcohols  and  acids  is  as  follows: 

Acetic  acid+methyl  alcohol  67.5,  benzoic  acid+methyl 
alcohol  64.5. 

Acetic  acid  +ethyl  alcohol  66.9,  benzoic  acid  -fethyl  alcohol  67. 

Acetic  acid  +amyl  alcohol  68.9,  benzoic  acid  +amyl  alcohol  70. 


178  ORGANIC  CHEMISTRY 

increased  by  removing  the  water  formed  during 
the  reaction,  and  in  some  cases  this  can  be  accom- 
plished. By  removing  the  ethereal  salt  as  it  is 
formed  (e.g.,  by  distillation  or  crystallization), 
much  higher  yields  can  also  be  obtained  (see  exp., 
p.  181). 

Preparation  of  Ethereal  Salts.  The  more  usual 
methods  for  preparing  ethereal  salts  are  the  follow- 
ing: 

1.  By  heating  a  mixture  of  the  acid  and  alcohol 
with   sulphuric   acid:    ethylsulphuric   acid  is  first 
formed  and  then  reacts  with  the  acid,  sulphuric 
acid  being  re-formed  (cf.  ether,  p.  134),  thus: 

(a)  C2H5|OH+H  .HS04  =  C2H5-HS04+H20. 

(6)  C2H5i^HS^+|[loOCCH3  = 

C2H5— OOC  •  CH3  +H2S04. 

2.  By  heating  a  mixture  of  the  acid  and  alcohol 
with  hydrochloric   acid  gas:    an  acid  chloride  is 
probably  first  formed,  which  then  reacts  with  the 
alcohol : 

(a)  CH3COJOH  +H|C1  =CH3CO  •  Cl  +H20. 

(6)  CH3CO|a +H|OC2H5  =  CH3COO  -  C2H5  +HC1. 

3.  Or  the  second  stage  of  this  reaction  (6)  can  be 
itself  used  for  the  production  of  ethereal  salts  by 
treating  an  alcohol  with  an  acid  chloride  or  an  anhy- 
dride of  an  acid.     In  this  latter  manner  the  acetyl 
or  benzoyl  (see  p.  359)  derivatives  of  many  sub- 
stances can  be  produced,  and  these,  being  readily 


FATTY  ACIDS  AND  ETHEREAL  SALTS          179 

purified,  are  extensively  prepared  for  purposes 
of  identification.  The  addition  of  sodium  hydroxide 
accelerates  this  reaction  in  the  case  of  benzoyl 
compounds  (see  p.  359). 

4.  By  treating  a  silver  salt  of  an  acid  with  an 
alkyl  halide  (as  iodide) ; 


CH3COO|Ag+I|C2H5  =CH3COOC2H5 +AgI. 

Properties.  Esters  in  a  pure  state  are  stable; 
in  watery  solution  they  slowly  decompose  into  acid 
and  alcohol,  the  decomposition  being  greatly  ac- 
celerated by  boiling  with  water  and  by  the  action 
of  acids  or  bases.  Hydrolysis  most  readily  occurs 
with  those  esters  which  are  easily  formed;  thus 
methyl  acetate  is  more  readily  formed  and  is  more 
easily  hydrolyzed  than  ethyl  acetate. 

Many  esters  have  pleasant  odors,  often  simulating 
those  of  fruits;  for  instance,  isoamyl  acetate  has  an 
odor  resembling  pears.  On  this  account  some  of 
them  are  used  as  artificial  fruit  essences  (see  p.  187). 

Ethereal  salts  include  the  neutral  fats  (see  p.  203). 
The  two  most  important  ethereal  salts  of  acetic  acid 
are  methyl  and  ethyl  acetates.  Prepared  by  the 
general  methods  described  above,  both  these  bodies 
are  liquids  with  pleasant  odors.  Ethyl  acetate  is 
commonly  called  acetic  ether. 

From  a  biochemical  standpoint  the  acceleration 
which  acids  induce  in  the  hydrolysis  of  esters  is  of 
interest,  partly  because  a  method  for  the  quanti- 
tative determination  of  the  acid  in  gastric  juice  is 
based  on  it,  and  partly  because  it  typifies  catalytic 


180  ORGANIC  CHEMISTRY 

action ,  which  is  the  means  by  which  enzymes  pro- 
duce their  actions.  Enzymes  have  a  much  more 
powerful  action  than  other  catalysts. 

Catalysis  is  defined  as  consisting  in  acceleration  of 
reactions,  which  would  take  place  without  the  cata- 
lyzer, but  more  slowly.  (Some  catalytic  agents 
cause  retardation  of  reactions.)  Neither  the  acid 
molecule  nor  the  ions  enter  into  the  chemical  reac- 
tion. When  a  chemical  agent  enters  into  the  reac- 
tion and  is  recovered,  as  sulphuric  acid  in  ether 
production,  it  is  a  pseudo-catalyst. 

If  equimolecular  quantities  of  different  acids  be 
added  to  similar  quantities  of  methyl  acetate,  it 
will  be  found  that  the  acceleration  of  hydrolysis 
produced  varies  greatly  with  the  acid  employed. 
HC1  and  HNOs  produce  about  the  greatest  accelera- 
tion, whereas  the  commonest  organic  acids  have 
only  a  feeble  influence;  thus  the  accelerating  influ- 
ence of  oxalic  acid  is  only  19%  and  of  acetic  only 
0.4%  of  that  of  HC1  (see  table  in  Appendix,  p.  452). 
Now  it  has  been  found  that  the  electrical  conduc- 
tivity of  dilute  solutions  of  the  acids  is  directly 
proportional  to  their  accelerating  (catalytic)  power, 
which  leads  us  to  the  conclusion  that  the  catalytic 
power  depends  on  the  amount  of  dissociation  which 
the  acids  undergo;  in  other  words,  on  the  number  of 
hydrogen  ions  existing  in  the  solution  (see  p.  172). 

By  this  means,  therefore,  we  have  a  practical 
method  for  gauging  the  relative  strengths  of  acids 
(see  p.  184). 

Further,  if  we  add  dilute  solutions  of  varying  con- 
centrations of  the  same  mineral  acid  to  methyl 


FATTY  ACIDS  AND  ETHEREAL  SALTS         181 

acetate  it  will  be  found  that  the  rate  of  hydrolysis 
is  proportional  to  the  strength  of  acid  added.  It 
is  important  to  note  that  this  law  holds  only  for 
dilute  solutions  (less  than  decinormal)  of  strong 
acids  and  not  at  all  for  weak  acids.  By  comparing 
the  amount  of  hydrolysis  of  methyl  acetate  that 
occurs  when  a  known  quantity  of  acid  is  added, 
with  the  amount  occurring  in  a  similar  solution  of 
methyl  acetate  having  an  unknown  quantity  of  the 
same  acid,  an  estimate  can  be  made  of  the  amount 
of  acid  actually  present  in  the  latter.  In  this 
comparison  the  two  solutions  must  of  course  be 
kept  at  the  same  temperature  and  the  action 
allowed  to  proceed  for  the  same  length  of  time 
(see  exp.  below), 

EXPERIMENTS.  (1)  Put  into  a  medium-sized  flask 
10  c.c.  of  alcohol  and  10  c.c.  of  C.P.  H2S04.  Use  a 
three-hole  cork;  by  one  hole  suspend  a  dropping 
funnel,  by  another  connect  with  a  condenser,  and 
insert  a  thermometer  so  that  its  bulb  is  in  the 
liquid.  Heat  until  the  liquid  is  at  135°,  then  begin 
running  in  slowly  by  the  dropping  funnel  a  mixture 
of  80  c.c.  of  alcohol  and  80  c.c.  of  glacial  acetic  acid, 
keeping  the  temperature  of  the  mixture  constant 
at  about  135°.  Regulate  the  inflow  of  acid  alcohol 
to  correspond  approximately  to  the  rate  of  dis- 
tillation. Wash  the  distillate  in  the  receiving 
flask  with  small  portions  of  saturated  sodium  car- 
bonate solution  until  the  top  layer  is  no  longer  acid 
to  litmus.  Separate  with  a  separating  funnel. 
Add  to  the  acetic  ether  a  cold  solution  of  20  gm. 


182  ORGANIC  CHEMISTRY 

of  calcium  chloride  in  20  c.c.  of  water  and  shake. 
(The  ester  is  soluble  in  17  parts  of  water).  Separate 
with  the  funnel.  Put  the  ethyl  acetate  into  a  dry 
flask,  add  solid  calcium  chloride,  cork,  and  let  it 
stand  a  day  or  so.  Redistill  on  a  water  bath,  noting 
the  boiling-point  (77°).  Determine  the  specific 
gravity  (0.905  at  17°). 

(2)  Determine  the  rate  of  hydrolysis  of  methyl 
acetate  as  influenced  by  different  strengths  of  acid 
(HC1).  Into  each  of  two  small  flasks  put  1  c.c.  of 
methyl  acetate  measured  accurately  with  a  pipette; 
to  one  add  with  a  pipette  20  c.c.  of  HC1  solution 
of  known  strength  (say  0.4%);  to  the  other  add 
20  c.c.  of  HC1  more  dilute  but  of  unknown  concen- 
tration; cork  each  flask  and  shake.  As  quickly 
as  possible  titrate  5  c.c.  of  each  mixture  successively 
with  decinormal  NaOH,  using  phenolphthalein  as 
an  indicator.  This  gives  the  acidity  of  each  at  the 
beginning  of  the  experiment.  Cork  the  flasks 
tightly  with  rubber  stoppers  and  keep  them  in  an 
incubator  at  about  40°  for  three  or  four  hours; 
then,  after  shaking  and  cooling,  take  5  c.c.  from  each 
and  titrate  again.  The  increase  in  acid  (due  to 
liberation  of  acetic  acid  by  hydrolysis)  is  found  by 
deducting  the  initial  titration  from  this  second 
titration.  The  stronger  solution  causes  the  greater 
amount  of  hydrolysis.  To  calculate  the  exact 
strength  of  the  unknown  acid  solution  by  com- 
parison with  the  known,  we  must  find  out  the  limit 
of  hydrolysis  for  the  known  strength;  to  do  this 
leave  the  flask  containing  this  acid  in  the  incubator 
for  forty-eight  hours,  then  titrate  again.  The 


FATTY  ACIDS  AND  ETHEREAL  SALTS         183 

titration  at  the  end  of  this  period,  less  the  initial 
titration,  gives  an  acid  value  called  A]  this  is  the 
number  of  cubic  centimeters  of  decinormal  acetic 
acid  that  can  be  liberated  by  hydrolysis  of  the 
methyl  acetate  by  0.4%  HCl.  Now  we  can  reckon 
the  per  cent  of  HCl  in  the  other  solution  in  the 
following  manner:  Find  the  value  of  the  constant 

/    A    \ 
in  the  formula  C=log  (    —  =     for  each  solution, 


but  call  the  constant  of  the  known  solution  Cf. 
The  observed  increase  in  acid  content  during  the 
three  or  four  hours'  incubation  is  X. 

Take  a  particular  experiment.  A  known  solu- 
tion (0.43435%  HCl)  gave  A  =24.9  (c.c.).  The 
increase  (after  four  hours)  in  the  known  solution 
was  12.1  (c.c.);  therefore  A  -X=  24.9  -12.1  =12.8: 


With  the  unknown  solution  X  =  7  (c.c.)  ,  A  -X  =  17.9  : 


Now  the  per  cent  of  HCl  in  the  unknown 
fC  of  unknownX 


"  of  known  / 


(per  cent  HCl  in  known). 


Therefore  per  cent  =   '  (0.43435)  =0.21544. 

\.2o7o/ 

In   this   particular    case    the   unknown   was   of 
exactly  half  the  strength  of  the  known  solution. 


184  ORGANIC  CHEMISTRY 

The  rate  of  hydrolysis  bears  a  definite  relation 
to  the  number  of  hydrogen  ions  present  in  the  solu- 
tion. Therefore  with  dilute  solutions  of  easily 
ionizable  acids  an  accurate  estimation  of  the  quantity 
of  acid  present  can  be  made  by  this  method.  Most 
organic  acids  furnish  so  few  hydrogen  ions  (see  p. 
157)  that  their  presence  has  practically  no  effect. 
In  consequence,  the  method  is  available  for  determin- 
ing the  per  cent  of  HC1  present  in  gastric  juice  or 
stomach  contents. 

It  must  not  be  forgotten,  however,  that  the  pres- 
ence of  salts  (as  in  stomach  contents)  can  change  the 
rate  of  hydrolysis  from  what  it  would  be  if  only  pure 
acid  were  present. 

EXPERIMENT  3.  Determine  the  relative  strength 
of  several  acids,  repeating  the  procedure  of  experi- 
ment 2.  Decinormal  solutions  of  tartaric,  oxalic, 
trichloracetic  and  hydrochloric  acids  give  interest- 
ing results.  Ethyl  acetate  may  be  used  instead  of 
methyl  acetate.  Make  a  third  titration  of  acidity 
after  hydrolysis  has  proceeded  for  at  least  a  day. 
Compare  directly  the  c.c.  increase  of  decinormal 
acid  in  the  various  mixtures.  This  will  give  a 
rough  idea  of  the  relative  H  ion  concentrations. 

OTHER  FATTY  ACIDS 

Propionic  acid  (propanoic  acid),  CHs-CH^-COOH, 
resembles  acetic  acid.  It  can  be  prepared  by 
oxidation  of  propyl  alcohol,  by  hydrolysis  of  ethyl 
cyanide,  and  by  the  action  of  CCb  on  sodium-ethyl. 


FATTY  ACIDS  AND  ETHEREAL  SALTS         185 

In  addition  it  can  be  made  by  reduction  of  lactic 
acid,  thus: 

CH3-CHOH-COOH+2HI    . 

=  CH3  -  CH2  •  COOH  +H20  +I2. 

The  hydriodic  acid  furnishes  nascent  hydrogen, 
and  this  brings  about  reduction. 

Corresponding  to  chloracetic  acids  there  are  chlor- 
propionic  acids.  But  the  halogen  may  take  the 
place  of  hydrogen  either  in  the  CH3  group  or  in  the 
CH2  group  of  propionic  acid.  It  becomes  neces- 
sary, therefore,  to  distinguish  between  these  two 
positions  in  the  molecule.  This  is  done  by  using 
Greek  letters,  a  and  /?.  In  order  to  have  a  rule 
that  will  apply  to  all  acids,  no  matter  how  many 
carbon  atoms  the  acid  may  contain,  it  is  necessary 
to  count  backwards  from  the  carboxyl  group: 
thus,  the  group  next  to  the  COOH  is  in  the  a  posi- 
tion, the  second  group  is  in  the  0  position,  and  so 
on;  for  example,  CH3-  CHOI-  COOH  is  a-chlor- 
propionic  acid,  CH2C1-CH2-COOH  is  p-chlor- 
propionic  acid. 

Butyric  acid  CH3  •  CH2  -  CH2  •  COOH,  is  normal 
butyric  acid. 

Isobutyric  acid  or  methylpropanoic  acid  has  the  f  or- 


mula  >CH  —  COOH.     Normal     butyric    acid 


is  fermentation  butyric  acid,  and  occurs  in  Lim- 
burger  cheese,  rancid  butter,  and  sweat.  It  may 
be  prepared  by  oxidation  of  butyl  alcohol  and  by 
hydrolysis  of  propyl  cyanide.  Butter  contains 


186  ORGANIC  CHEMISTRY 

about  6%  of  butyrin,  which  is  the  glycerol  ester  of 
butyric  acid  (see  p.  200)  ;  the  acid  can  therefore  be 
obtained  by  hydrolysis  or  saponification  of  butter 
(see  exp.,  p.  207).  Microorganisms  can  cause 
fermentation  of  butter,  with  resulting  hydrolysis 
of  the  ester  (butyrin)  and  setting  free  of  butyric 
acid.  Butyric  acid  is  soluble  in  water  and  vola- 
tile. Oleomargarine  contains  very  little  butyric  or 
other  soluble  volatile  fatty  acids.  On  this  account 
it  can  readily  be  identified  by  making  an  estimation 
of  the  volatile  acids  in  the  manner  to  be  described 
later  in  an  experiment  (see  p.  207). 

Butyric  acid  can  also  be  made  from  cane  sugar  as 
follows:  The  sugar  solution,  acidified  with  tar- 
taric  acid,  is  inoculated  with  sour  milk:  one  variety 
of  microorganisms  in  the  latter  "  inverts  "  the 
sugar  into  dextrose  and  Isevulose;  another  variety 
ferments  these  monosaccharides,  producing  lactic 
acid;  while  a  third  variety  converts  the  lactic 
acid  into  butyric  acid: 


(Cane  sugar)  (Dextrose)  (Laevulose) 


(Lactic  acid) 

2C3H603  =  CH3  •  CH2  •  CH2  •  COOH  +2CO2  +2H2. 

(Butyric  acid) 

Similar  fermentation,  with  production  of  lactic  and 
butyric  acids,  may  occur  in  the  stomach  when  the 
hydrochloric  acid  of  the  gastric  juice  is  deficient 
in  amount  or  absent  altogether.  The  gases  formed 
and  H2)  cause  the  flatulence  present  in  such 


FATTY  ACIDS  AND  ETHEREAL  SALTS          187 

cases.  Butyric  acid  has  the  peculiar  disagreeable 
odor  characteristic  of  rancid  butter. 

The  ethereal  salt  C3H7-COOC2H5,  ethyl  butyrate, 
resembles  pineapple  in  odor.  It  is  used  as  a  flavor- 
ing material  in  place  of  pineapple  juice. 

Valeric  acid  (valerianic  acid), 

CH3  -  CH2  -  CH2  •  CH2  •  COOH, 

is  the  normal  acid.     Ordinary  valeric  acid,  however, 

CH3v 

is     isovaleric     acid,  ">CH  •  CH2  •  COOH.     It 

/ 


occurs  in  valerian  root. 

Amyl  valerate,  CJETg-COOCsHn,  smells  like  apple, 
and  is  therefore  used  as  an  apple  essence.  This  is 
the  ester  of  isoamyl  alcohol  with  isovaleric  acid.  It 
has  been  used  as  a  medicine. 

Of  the  other  acids  of  the  formic  acid  series,  only 
those  containing  an  even  number  of  CH2  groups  are 
of  importance. 

Capnric  acid  is  CH3(CH2)4COOH. 
Caprylic  acid  is  CH3(CH2)6COOH. 
Capric  acid  is  CH3(CH2)8COOH. 
Laurie  acid  is  CH3(CH2)10COOH. 
Myristic  acid  is  CH3(CH2)i2COOH. 
Palmitic  acid  is  CH3(CH2)i4COOH. 
Stearic  acid  is  CH3(CH2)16COOH. 
Arachidic  acid  is  CH3(CH2)i8COOH. 
Behenic  acid  is  CH3(CH2)20COOH. 

Most  of  these  occur  in  fats.  The  lowest  acids  are 
volatile  with  steam  and  soluble.  The  higher  acids 


188  ORGANIC  CHEMISTRY 

are  non-volatile  and  insoluble.  The  melting-point 
of  palmitic  acid  is  62.6°,  and  of  stearic  acid  is  69.2°. 
The  calcium  salt  of  monoiodo-behenic  acid  is  a 
remedy  called  sajodin;  it  is  used  for  administra- 
tion of  iodine. 


CHAPTER  XIII 

SECONDARY  AND  CERTAIN  OTHER  MONACID 
ALCOHOLS.    KETONES 

SECONDARY  ALCOHOLS  AND   THEIR  OXIDATION 
PRODUCTS 

SECONDARY  alcohols  contain  the  group  CHOH,  as 
in  CHs  •  CHOH  •  CH3,  secondary  propyl  alcohol.  None 
of  the  secondary  alcohols  is  of  any  importance. 

When  a  secondary  alcohol  is  oxidized  an  aldehyde 
is  not  formed,  but  a  ketone: 

CH3  •  CHOH  •  CH3  +O  =  CH3  •  CO  -  CH3  +H20 
or 


A  ketone  is  in  all  essential  points  identical  with  an 
aldehyde,  the  only  difference  being  that  in  the  case 
of  an  aldehyde  the  oxygen  atom  is  attached  to  a 
carbon  atom  at  one  end  of  the  chain,  while  in  a 
ketone  it  is  attached  to  an  inner  carbon  atom. 
Some  ketones  can  be  oxidized,  but  this  involves 
splitting  up  the  chain  of  carbon  atoms.  Some 
ketones  give  the  fuchsin  test  (see  p.  154),  particularly 

189 


190  ORGANIC  CHEMISTRY 

those  that  have  CH3  •  CO  in  the  molecule.  Many 
ketones  form  addition  compounds  with  acid  sul- 
phites and  with  hydrocyanic  acid  (cf.  aldehydes). 
Phenylhydrazine  reacts  with  ketones  in  the  same 
manner  as  with  aldehydes,  forming  hydrazones. 
Ketones  do  not  polymerize,  but  they  form  condensa- 
tion products. 

The  reaction  of  phosphorus  pentachloride  with 
ketones  is  similar  to  that  with  aldehydes: 

CH3  •  CO  •  CHS  +PC15  =  CH3  •  CC12  -  CH3  +POC13. 

No  hydrochloric  acid  is  produced,  and  a  dichlor 
derivative  is  formed;  therefore  a  ketone  does  not 
contain  hydroxyl.  The  most  important  ketone  is 
acetone. 

Acetone  (dimethylketone  or  propanone)  is  the  sim- 
plest ketone,  its  formula  being  CH3-CO-CH3.  It 
is  produced  commercially  by  the  dry  distillation 
of  calcium  acetate  at  about  300°: 

CH3— C< 

*  ~   =CH3-CO-CH3+CaC03. 


It  can  also  be  obtained  by  oxidation  of  secondary 
propyl  alcohol.  Its  synthesis  from  zinc  methyl  and 
acetyl  chloride  proves  the  structural  formula  for 
acetone. 


CH, 

CH3-CO-|C1_          J\CH3 

=2CH3-CO-CH3+ZnCl2. 


SECONDARY  ALCOHOLS  AND  KETONES         191 

Acetone  is  present  in  the  urine  under  certain  con- 
ditions, especially  in  severe  cases  of  diabetes.  It  is 
a  useful  solvent.  It  is  a  liquid,  boiling  a  t56.3° 
(corrected),  with  a  specific  gravity  of  0.812  at  0°. 
Nascent  hydrogen  converts  it  into  secondary  pro- 
pyl  alcohol.  It  does  not  oxidize  to  an  acid  contain- 
ing the  same  number  of  carbon  atoms,  but  to  acetic 
and  formic  or  carbonic  acids.  Acetone  gives  the 
iodoform  test. 

EXPERIMENTS.  (1)  Make  iodoform,  using  ace- 
tone instead  of  alcohol  (see  p.  130). 

The  reactions  involved  are  of  the  same  nature  as 
in  the  preparation  of  iodoform  from  alcohol;  in  this 
case  the  intermediate  compound  is  triiodoacetone, 
CI3-CO-CH3. 

(2)  Dissolve  2  c.c.  of  acetone  in  dilute  H2S04,* 
add  KMn(>4  solution  until  a  pink  color  remains  on 
warming.     Filter,  make  the  filtrate  strongly  acid 
with  20%  H2S04,  and  distill.     Test  the  distillate  for 
acetic  acid  (see  p.  163). 

(3)  Shake   5   c.c.   of   acetone  with   8   c.c.   of   a 
saturated    solution    of    sodium    bisulphite;     cool; 
crystals  of  the  addition  compound  of  acetone  appear. 
Filter  and  wash.     Save  samples. 

Chloretone  (chloroform  acetone,  trichlor-tertiary- 

/O— H 

butyl-alcohol),  CH3 — (Xj- CC13,  is  an  addition 

XCH3 

product  of  acetone.  It  is  formed  by  the  interaction 
of  acetone  and  chloroform  in  the  presence  of  an  excess 
of  KOH,  It  is  a  useful  hypnotic. 


192  ORGANIC  CHEMISTRY 

Brometone,  the  corresponding  bromine  prepara- 
tion, produced  from  acetone  and  bromoform,  is 
analogous  to  chloretone.  As  a  remedy  it  is  used 
instead  of  bromides. 

Ketone  acids.  Some  acids  contain  both  the  car- 
bony!  and  carboxyl  groups.  Aceto-acetic  acid, 
CH3-CO-CH2-COOH,  typifies  these,  and  is  of 
importance,  since  it  may  occur  in  the  urine  (see 
p.  218). 

Pyruvic  acid  (pyroracemic  acid)  is  another 
ketone  acid  of  importance.  Its  formula  is 
CH3-CO-COOH.  It  shows  a  strong  tendency  to 
polymerize. 

Tertiary  alcohols,  when  oxidized,  decompose  into 
compounds  containing  fewer  carbon  atoms  than  the 
alcohol.  The  tertiary  alcohols  are  of  no  importance. 

Little  need  be  said  of  other  monacid  alcohols, 
except  that  most  waxes  contain  esters  of  monacid 
alcohols  having  a  large  number  of  carbon  atoms;  for 
example : 

Ceryl  alcohol,  C26H530H. 

Cetyl  alcohol,  CH3(CH2)i4CH2OH. 

Melissic  alcohol,  C3oH6iOH. 

In  waxes  some  of  the  alcohol  is  not  in  ester  com- 
bination, but  free. 

Cetyl  palmitate  has  been  found  in  the  fat  of  an 
ovarian  cyst.  Lanolin  contains  -some  wax  esters 
(see  p.  211). 

Myricyl  palmitate,  C3oH6iOOC-Ci6H3i,  is  the 
chief  constituent  of  beeswax, 


CHAPTER  XIV 

DIACID  ALCOHOLS  AND  DIBASIC  ACIDS 
DIACID  ALCOHOLS 

DIACID  alcohols  contain  two  hydroxyl  groups. 
They  are  comparable  to  Ca(OH)2.  The  simplest 
diacid  alcohol,  and  the  only  one  of  importance,  is 

glycol  (ethandiol),    CH2OH 

.    The  method  of  prep- 
CH2OH 

aration  shows  that  both  hydroxyl  groups  are  not 
attached  to  the  same  carbon  atom.  Ethylene  is 
produced  from  ethyl  alcohol  by  heating  the  latter 
with  an  excess  of  sulphuric  acid.  The  ethylene  is 
saturated  with  bromine,  forming  ethylene  bromide, 
in  the  manner  described  in  the  experiment  (see 
p.  301).  From  ethylene  bromide  glycol  can  be 
obtained  by  the  action  of  silver  hydroxide: 


AOH    CH2OH 

I         "  ±  ......         =  I  +2AgBr. 

CH2jBr    AglOH    CH2OH 

Glycol  is  a  colorless  glycerol-like  liquid,  of  sweet- 
ish taste.  It  boils  at  195°  and  has  a  specific  gravity 
of  1.128  at  0°. 

It  forms  two  classes  of  ethereal  salts,  according 

193 


194  ORGANIC  CHEMISTRY 

to  whether  one   or  both  hydroxyls  are   replaced. 
Similarly  there  are  two  sodium  alcoholates  of  glycol: 

CH2ONa 

,  monosodium  glycolate,1  and 
CH2OH 

CH2ONa 

,  disodium  glycolate. 
CH2ONa 

The  oxidation  products  of  glycol  are  numerous 
because  of  the  presence  of  two  primary  alcohol 
groups.  There  are  two  aldehydes: 


•^>- 

|  ,  glycolic  aldehyde,  and 

V_y- 


CH2OH 
JHO 

CHO 

I       ,  glyoxal. 
CHO 

Oxidation  of  the  first  gives  rise  to  glycollic  acid, 
CH2OH 

;    this  will  be  considered  under    hydroxy- 
COOH 
acids    (see   p.    212).    Oxidation    of   glyoxal    gives 

CHO 

,  glyoxylic  acid;    this  is  really  a  dihydroxy- 
COOH 

acid,  as  will  be  seen  later  (see  p.  219).     These  two 
acids  are  monobasic.     Complete  oxidation  of  glycol 

1  Distinguish  from  the  glycollates  derived  from  glycollic  acid 
(p.  213). 


DIACID  ALCOHOLS  AND  DIBASIC  ACIDS       195 

results  in  the  formation  of  a  dibasic  acid,  oxalic  acid, 
COOH 

GOGH* 

DIBASIC  ACIDS 

The  simplest  is  oxalic  acid.    The  next  members 

/COOH 

of  the  series  are  malonic  acid,  CH2<T  ~~  .-„  >  succinic 

M^OOJci 

CH2— COOH 

acid,   |  ,  and  glutaric  acid, 

CH2— COOH 

/CH2— COOH 

H2\CH2— COOH* 

General  methods  for  the  production  of  dibasic 
acids  are  (1)  by  hydrolysis  of  cyan-acids,  (2)  by 
oxidation  of  diacid  alcohols,  and  (3)  by  oxidation  of 
an  Itydroxy-acid. 

The  acids  of  the  oxalic  acid  series  show  the  same 
behavior  as  regards  melting-points  as  do  the  acids  of 
the  formic  acid  series  (see  p.  158). 
COOH 

Oxalic  acid,  I  ,  forms  crystals  containing  two 

COOH 

molecules  of  water  for  each  molecule  of  oxalic  acid. 
The  crystals  readily  effloresce.  It  may  be  prepared 
by  oxidation  of  cane  sugar  with  nitric  acid.  It 
was  formerly  made  by  heating  sawdust  with  caustic 
potash  and  soda.  After  cooling  the  oxalate  is  dis- 
solved out  of  the  mass,  precipitated  by  slaked  lime 
as  calcium  oxalate,  and  the  separated  oxalate  is 
treated  with  sulphuric  acid,  so  that  the  oxalic  acid 
is  set  free.  It  is  now  made  by  heating  together 


196  ORGANIC  CHEMISTRY 

potassium  formate  and  hydroxide  (and  a  little 
oxalate);  and  treating  the  product  with  sulphuric 
acid.  Oxalic  acid  is  one  of  the  strongest  of  all 
organic  acids,  because  its  solution  contains  more 
hydrogen  ions  than  the  corresponding  solutions  of 
most  other  organic  acids  (see  p.  172). 

As  the  number  of  C  atoms  interposed  between  the 
carboxyls  of  acids  of  this  series  is  increased,  acid 
power  is  decreased. 

When  oxalic  acid  is  heated,  it  first  loses  its  water  of 
crystallization,  then  decomposes  into  carbon  dioxide, 
carbon  monoxide,  water,  and  some  formic  acid.  If 
heated  in  the  presence  of  glycerol,  formic  acid  and 
carbon  dioxide  are  formed  (see  p.  159).  Sulphuric 
acid  decomposes  it  to  carbon  monoxide,  carbon 
dioxide,  and  water.  Potassium  permanganate  in 
warm  acid  solution  oxidizes  it  to  carbon  dioxide  and 
water: 

2KMnO4  +5(COOH)2  +3H2S04  =  10C02  +K2S04 

+2MnSO4+8H2O. 

Oxalic  acid  forms  two  classes  of  salts,  acid  and 

COOH 
neutral.    Acid   potassium    oxalate,     \  ,    occurs 

COOK 

in  plants,  particularly  sorrel.  Ammonium,  potas- 
sium, and  sodium  oxalates  are  soluble;  all  other 
oxalates  of  metals  are  practically  insoluble.  Cal- 
cium oxalate  frequently  occurs  in  the  urine  as  a 
crystalline  sediment. 

Oxalic  acid  is  poisonous  and  has  been  used  for 
suicidal  purposes. 


DIACID  ALOCOHLS  AND  DIBASIC  ACIDS        197 

EXPERIMENTS.  (1)  Preparation  of  oxalic  acid. 
Heat  200  c.c.  of  HN03  in  a  large  flask  to  100°. 
Set  in  a  fume-closet  and  add  50  gm.  of  cane  sugar. 
When  the  evolution  of  fumes  has  ceased,  evaporate 
the  acid  mixture  in  an  evaporating  dish  to  about 
one  third  its  original  volume.  Cool  and  collect  the 
crystals.  Recrystallize,  using  as  little  hot  water 
as  possible. 

(2)  Heat  some  dry  crystals  of  oxalic  acid  in  a 
test-tube,   loss  of  water  of  crystallization  occurs, 
as  shown  by  drops  collecting  on  the  cool  part  of  the 
tube. 

(3)  Decompose   some   oxalic   acid   with   H2SO4; 
test  the  evolved  gases  for  CO2  (baryta  water,  as 
on  p.  3)  and  CO  (haemoglobin  solution,  as  on  p. 
161). 

(4)  To  5  c.c.  of  oxalic  acid  solution  add  a  few  drops 
of  H2SO4,  warm,  then  add  potassium  permanganate 
solution,  it  is  decolorized. 

/COOH 

Malonic    acid,    CH2<T  ,    is    of    importance 

\COOH 

mainly  in  bringing  about  certain  organic  syntheses. 

CH2— COOH 
Succinic    acid,     |  ,   is  normal   succinic 

CH2— COOH 

acid  and  may  be  produced  by  hydrolysis  of  /3-cyan- 
propionic  acid: 

CH2CN  •  CH2  •  COOH  +2H20  =  CH2— COOH 

+NH3. 
CH2— COOH 

If  caustic  potash  is  used  to  effect  hydrolysis,  potas- 
sium succinate  would  be  formed. 


198  ORGANIC  CHEMISTRY 

If  <*-cyanpropionic  acid  be  hydrolyzed,  isosuccinic 
acid  is  formed : 


CH3  -  CHCN  -  COOH  +2H2O  =  CH3  +NH3. 

CH< 


/COOH 


\COOH 

These  two  acids  give  different  reactions. 

Normal  succinic  acid  when  heated  to  235°  yields 
succinic  anhydride  and  water: 

COOH  -  CH2  •  CH2  •  COOH  =  CH2— COX 

|  >0+H20. 

CK2—CO/ 

(Succinic  anhydride) 

Isosuccinic  acid,  however,  when  heated  above  130°, 
breaks  up  into  propionic  acid  and  carbon  dioxide: 

/COOH 
CH3  •  CH\COOH  =  CH3  •  CH2  -  COOH  +C02. 

It  is,  indeed,  a  general  rule  in  organic  chemistry  that 
two  carboxyl  groups  cannot  remain  attached  to  the 
same  carbon  atom  at  high  temperatures,  carbon 
dioxide  being  split  off  from  one  of  the  carboxyls. 

Alphozone    (disuccinyl    peroxide)    is    an    organic 
peroxide  (cf .  acetozone  p.  352) : 

HOOC(CH2)2CO— O— O— OC(CH2)2COOH. 
It  is  an  oxidizing  agent,  and  is  said  to  be  antiseptic. 


CHAPTER  XV 

TRIACID  ALCOHOLS,  FATS,  AND  SOAPS 
TRIACID  ALCOHOLS 

CH2OH 
Glycerol  (glycerine  or  propanetriol),  | 

CHOH,  is  the 


.2OH 

only  triacid  alcohol  of  importance.  Glycerol  occurs 
in  fats  in  combination  with  fatty  acids  and  oleic 
acid,  as  glycerol  esters  of  these  acids.  By  hydrolyz- 
ing  fats,  glycerol  is  set  free.  This  is  accomplished 
commercially  by  heating  fats  (at  170-180°)  in 
a  closed  boiler  or  autoclave  with  water  and  lime. 
The  lime  combines  with  fatty  acids,  forming  insolu- 
ble calcium  salts,  while  the  glycerol  goes  into 
solution.  The  calcium  remaining  in  solution  is 
precipitated  with  sulphuric  acid.  Glycerol  is  also 
a  by-product  of  soap  manufacture.  The  liquid 
left  after  the  separation  of  hard  soap,  containing 
4-5%  of  glycerol,  is  purified  to  remove  salts  and 
alkali.  The  dilute  glycerol  solution  is  then  evapor- 
ated under  diminished  pressure,  at  as  low  a  tem- 
perature as  possible,  until  its  specific  gravity 
becomes  1.24.  The  crude  glycerol  is  purified  by 
combined  steam  and  vacuum  distillation.  C.P. 
glycerol  is  prepared  by  treatment  of  distilled 

199 


200  ORGANIC  CHEMISTRY 

glycerol  with  charcoal  and  distillation  with  steam  in 
vacuo. 

Glyceryl  butyrate  or  butyrin  yields  on  hydrolysis 
glycerol  and  butyric  acid,  thus: 

CH2— OOC  •  C3H7  CH2OH 

CH  —OOC  -  C3H7+  3H20 = CHOH  +3C3H7  •  COOH. 
I  I 

CH2— OOC  -  C3H7  CH2OH 

The  other  fats  will  be  considered  more  fully  pres- 
ently. 

Pure  glycerol  is  a  colorless,  syrupy  liquid,  hav- 
ing a  sweet  taste.  It  boils  at  290°  and  has  a  spe- 
cific gravity  of  1.265  at  15°.  It  is  hygroscopic. 
Crystals  of  glycerol  can  be  obtained  by  cooling  to 
a  low  temperature  (0°);  these  melt  at  17°.  It  is 
volatile  with  water-vapor.  It  is  useful  as  a  solvent 
and  as  a  preservative  agent. 

One,  two,  or  three  of  the  hydroxyl  groups  can  be 
replaced  by  chlorine  to  form  mono-,  di-,  or  trichlor- 

CH2C1  CH2C1  CH2C1 

hydrin        respectively:    CHOH,     CHOH,     CHC1 


A, 


CH2C1  CH2C1. 
If  trichlorhydrin  be  heated  with  water  to  170°,  it  is 
hydrolyzed  to  glycerol.  Glycerol  can  be  obtained 
from  ethyl  alcohol  by  producing  successively  acetic 
acid,  acetone,  isopropyl  alcohol,  propylene,  pro- 
pylene  dichloride,  trichlorhydrin,  and,  finally, 
glycerol : 


TRIACID  ALCOHOLS,  FATS,  AND  SOAPS       201 
CH3  •  CH2OH  ->  CH3COOH  ->  CH3  •  CO  •  CH3  -> 

(Alcohol)  (Acetic  acid)  (Acetone) 

~>  CH3  •  CHOH  •  CH3  -»  CH3  -  CH— CH2  -> 

(Isopropyl  alcohol)  (Propylene) 

->  CH3  •  CHC1  -  CH2C1  ->  CH2C1  •  CHC1  •  CH2C1  -> 

(Propylene  dichloride)  (Trichlorhydrin) 

-»  CH2OH  •  CHOH  •  CH2OH. 

(Glycerol) 

Glycerol  forms  salts  with  nitric  acid.  The  tri- 
nitrate  is  nitroglycerine  or  nitroglycerol.  It  is  a 
yellow,  oily  liquid,  made  by  mixing  glycerol  with 
sulphuric  and  nitric  acids.  When  the  action  has 
ceased,  the  mixture  is  poured  into  a  large  volume 
of  cold  water;  the  nitroglycerine  separates  as  a 

CH2— 0— N02 

I 
heavy  oil.     Its  formula  is  CH  — 0 — N02.     It  ex- 

CH2— 0— NO2 

plodes  when  suddenly  heated  or  percussed,  with  the 
formation  of  nitrogen,  nitric  oxide,  carbon  dioxide, 
and  water.  Dynamite  consists  of  infusorial  earth 
or  other  material  impregnated  with  nitroglycerol, 
and  may  contain  as  much  as  75%  of  the  latter. 

Nobel  discovered  that  nitrocellulose  (p.  247)  will 
absorb  nitroglycerine;  a  gelatinous  mass  being 
formed.  Such  explosives  as  cordite  and  ballistite 
are  prepared  in  this  way. 

Gelatin  dynamite  is  prepared  from  resin,  collodion 
gun-cotton,  a  little  wood  pulp,  and  nitroglycerol. 

Nitroglycerol  is  a  strong  poison,  causing  violent 


202  ORGANIC  CHEMISTRY 

headache  and  lowering  of  blood-pressure.     In  1% 
alcoholic  solution  it  is  used  as  a  medicine.1 

Tetranitrol  is  similar  to  nitroglycerol,  chemically  and  phar- 
macologically. It  is  the  tetranitrate  of  the  tetracid  alcohol 
erythrol. 

Glycerol  forms  glyceryl  acetates  when  treated  with 
acetic  anhydride.  This  will  be  considered  more 
fully  under  fats. 

COOH 

On  oxidation  glycerol  yields  gly eerie  acid,  CHOH, 

CH2OH 
COOH 

I 
and  tartronic  acid,  CHOH.     These  are  studied  with 


COOH 


the  hydroxy-acids  (see  pp.  219  and  221). 

Glycerophosphoric  acid  consists  of  one  molecule 
of  orthophosphoric  acid  combined  with  glycerol, 
CH2OH  •  CHOH .  CH2(H2P04). 

EXPERIMENTS.  (1)  Heat  1  c.c.  of  glycerol  with  5 
gm.  of  KHSO4  in  an  evaporating  dish  until  it  turns 
brown.  Note  the  odor  (acrolein)  (see  p.  302). 
The  fumes  will  blacken  a  strip  of  paper  that  has 
been  moistened  with  ammoniacal  silver  nitrate 
solution. 

(2)  Repeat  the  same  experiment,  using  lard  or 
some  other  fat.     Glycerol  in  combination  also  gives 
the  acrolein  test. 

(3)  To  a  few  cubic  centimeters  of  NaOH  solution 

1  This  is  nitrite  action  (cf.  amyl  nitrite,  p.  265). 


TRIACID  ALCOHOLS,  FATS,  AND  SOAPS         203 

add  CuSO*  until  a  copious  precipitate  of  Cu(OH)2  is 
obtained;  now  add  some  glycerol  and  shake,  a  deep- 
blue  solution  results. 

FATS  AND  SOAPS 

Fats  contain  esters  of  glycerol  with  fatty  acids 
and  with  the  unsaturated  acid,  oleic  acid.  Only 
those  members  of  the  fatty  acid  series  that  contain 
an  even  number  of  CH2  groups  in  then:  formulae, 
occur  in  fats.  Most  fats  are  mixtures  of  palmitin 
(glyceryl  tripalmitate),  stearin  (glyceryl  tristearate), 
and  olein  (glyceryl  trioleate).  Olein  is  a  liquid. 
Palmitin  melts  at  65°,  while  stearin  has  the  highest 
melting-point  (about  72°).  The  esters  of  low 
molecular  weight,  butyrin,  caproin,  caprylin,  (these 
three  are  liquids),  and  caprin  (melting  at  31°) 
are  peculiar  to  butter.  Mutton-fat  contains  a 
large  percentage  of  stearin.  Lard  contains  esters  of 
lauric,  myristic  and  linoleic  acids,  as  well  as  the 
commoner  esters.  The  softer  fats  contain  less 
stearin  and  palmitin  and  relatively  more  olein. 
Physiologically,  the  fats  of  lower  melting-point 
are  more  easily  digested. 

CH2— OOC-Ci5H3i 

Palmitin  is  CH  —  OOC-Ci5H3i. 

CH2— OOC-Ci5H3i 
CH2— OOC-Ci7H35 

in  is  C] 


Stearin  is  CH  — OOC-Ci7H35. 

-OOC  '  Cl7H35 


CH< 


204  ORGANIC  CHEMISTRY 


Mixed  esters  of  glycerol  can  be  obtained;  some  have 
been  proved  to  occur  naturally. 

CH2— OOC-Ci5H3i 


CH-OOC.Ci7H35 

CH.2 OOC  *  Ci7ll35 

is  a  mixed  ester. 

The  following  mixed  esters  have  been  detected 
in  beef  and  mutton  fat :  dipalmito-stearin,  dipalmito- 
olein,  palmito-distearin,  and  oleo-palmito-stearin. 

Butter  contains  glycerol  esters  of  fatty  acids  that 
are  volatile  and  soluble,  namely,  butyric,  capric, 
caprylic,  and  caproic  acids.  Artificial  butters  (as 
oleomargarine)  contain  only  very  small  amounts  of 
these  acids. 

Butter  also  contains  esters  of  myristic,  lauric  and 
dihydroxystearic  acids. 

It  will  be  of  interest  to  give  the  composition  of  the 
oils  that  are  used  most  commonly  in  medicine: 

Cod-liver  oil  contains  glycerides  of  palmitic, 
stearic,  oleic,  myristic,  erucic,  and  two  other  un- 
saturated  acids,  also  cholesterol. 

Croton  oil  contains  tiglic,  crotonic,  formic,  acetic, 
butyric,  valeric,  myristic,  and  lauric  acids,  besides 
palmitic,  stearic,  and  oleic  acids. 

Castor  oil  is  composed  chiefly  of  esters  of  ricinoleic 
and  isoricinoleic  acids,  and  contains  also  sebacic, 
stearic,  and  dihydroxystearic  acids. 

Olive  oil  has  olein  to  the  extent  of  70%,  and  con- 
tains also  esters  of  palmitic  and  arachidic  acids, 
and  some  phytosterol. 


TRIACJD  ALCOHOLS,  FATS,  AND  SOAPS        205 

Fat  Values.  By  determining  certain  analytical 
values 1  and  by  finding  the  melting-point  and  spe- 
cific gravity,  a  fat  can  generally  be  identified  with 
the  aid  of  the  tables  compiled  for  the  purpose. 
The  values  referred  to  will  now  be  briefly  explained 
in  order. 

(1)  The   Reichert-Meissl    number    indicates    the 
amount  of  volatile  soluble  acid  present  in  the  fat. 
When  butter  or  any  other  fatty  substance  is  saponi- 
fied so  as  to  free  the  fat  acid  and  then  distilled  as 
described   in   the   experiment   below,    the   volatile 
acid   in  solution  in  the  distillate  can  be  readily 
estimated  by  titration.     The  Reichert-Meissl  value 
is  the  number  of  cubic  centimeters  of  decinormal 
acid  contained  in  the  distillate  from  five  grams  of 
fatty  substance. 

(2)  The  acid  number  of  a  fat  is  found  by  titration 
of  a  solution  of  the  fat  in  alcohol  ether  mixture  with 
decinormal  KOH,   phenolphthalein  being  used  as 
an  indicator.     This  determines  the  amount  of  free 
acid  present.     The  acid  value  is  expressed  as  milli- 
grams of  KOH  required  to  neutralize  the  free  acids 
in  one  gram  of  fat. 

(3)  The  total  amount  of  acid  present,  free  and 
combined,  is  indicated  by  the  saponification  number. 
A  weighed  quantity  of  fat  (2-4  gm.)  is  saponified  by 
heating  it  with  an  accurately  measured  quantity 
of  alcoholic  KOH  solution  of  known  strength  (half 
normal);   the  resulting  soap  is  diluted  and  titrated 
with  half  normal  HC1  to  find  how  much    KOH 

XA  very  satisfactory  book  on  this  subject  is  Chemical 
Analysis  of  Oils,  Fats,  and  Waxes,  by  J.  Lewkbwitsch. 


206  ORGANIC  CHEMISTRY 

remains  unneutralized.  Then  the  amount  in  milli- 
grams of  KOH  combined  with  fatty  acid  as  soap 
for  each  gram  of  fat  taken  is  readily  calculated; 
this  is  the  saponification  number. 

(4)  The  ester  number  of  a  fat  represents  the  com- 
bined acid,  being  the  saponification  number  less  the 
acid  number. 

(5)  The  iodine  number  estimates  the  amount  of 
unsaturated  acid  (e.g.,  oleic)  present.    The  iodine 
forms  an  addition  compound  with  the  acid  (see  p. 
299).     This  value  is  expressed  as  the  grams  of  iodine 
taken  up  by  100  grams  of  fat. 

(6)  The   acetyl  number   estimates   the  hydroxyl 
content.     If  glycerol  is  treated  with  acetic  anhydride 
one  molecule  of  acetic  acid  is  produced  for  each 
hydroxyl  group  attached  (see  p.  169) : 

CH2|OH~~  """OC:CH51 
CHOH+O 

CH2OH         OC-CHs 

=  CH3  •  COOH +CH2  -  OOC  -  CH3 

CHOH 
CH2OH 

(Glyceryl  monacetate) 

The  reaction  can  be  pushed  until  all  of  the  hydroxyl 
groups  are  displaced,  giving,  as  the  products,  glyceryl 
triacetate  and  acetic  acid  (three  molecules  of  the 
latter  for  each  molecule  of  glycerol).  In  a  similar 
manner  a  fat  which  contains  some  hydroxyl  groups 
can  be  "  acetylated,"  and  by  estimating  the  acetic 


TRIACID  ALCOHOLS,   FATS,   AND  SOAPS        207 

acid  in  combination  with  the  alcohol,  or  acids  of 
the  fat,  the  hydroxyl  content  can  be  calculated. 
The  acetyl  number  is  the  number  of  milligrams 
of  KOH  required  to  neutralize  the  acetic  acid  after 
hydrolysis  of  one  gram  of  the  acetylated  fat.  Par- 
tially hydrolyzed  fat  esters  (e.g.,  a  diglyceride) 
and  hydroxy-acids  are  mainly  responsible  for  this 
number.  Such  an  acid  is  ricinoleic  acid  (p.  304) 
contained  in  castor  oil,  also  dihydroxy-stearic  acid, 
CH3(CH2)7(CHOH)2(CH2)7COOH,  which  is  pres- 
ent in  butter  and  in  castor  oil. 

The  viscosity  number  (see  p.  79)  may  be  deter- 
mined for  the  purpose  of  detecting  adulteration  of 
olive  oil,  since  the  cheaper  vegetable  oils  have  a 
lower  viscosity. 

EXPERIMENTS.  (1)  Compare  the  specific  gravity 
of  filtered  butter  with  that  of  oleomargarine  by  suc- 
cessively putting  a  little  of  each  in  alcohol  of  specific 
gravity  0.926  at  15°.  There  must  be  no  air  bubbles 
adhering  to  the  fat.  The  oleomargarine  will  float 
(it  having  a  specific  gravity  of  about  0.918  at  15°); 
the  butter  will  either  sink  or  remain  suspended. 

(2)  Reichert-Meissl  number.  Into  a  300-c.c.  flask 
put  5  gm.  of  filtered  butter,  2  c.c.  of  60%  KOH  solu- 
tion, and  20  c.c.  of  glycerol.  Heat  with  a  small 
flame,  shaking  to  prevent  excessive  foaming.  In 
about  five  minutes  the  water  is  boiled  off  and 
saponification  is  almost  complete.  Tip  the  flask 
and  rotate  to  bring  down  any  fat  adhering  to  the 
walls.  Heat  again  for  a  few  minutes,  then  partly 
cool.  The  soap  solution  should  be  clear.  Add 


208  ORGANIC  CHEMISTRY 

90  c.c.  of  hot  distilled  water  and  shake  until  the 
soap  is  dissolved.  Add  50  c.c.  of  5%  H2S04  and 
some  zinc  powder  or  small  pieces  of  pumice.1  Distill 
on  a  sand-bath.  Collect  110  c.c.  of  distillate  in  a 
graduated  flask.  The  distilling  should  be  accom- 
plished in  thirty  minutes.  Filter  the  distillate; 
take  100  c.c.  of  the  nitrate  with  a  pipette  and 
transfer  it  to  a  beaker.  Add  a  little  phenol- 
phthalein  solution  and  titrate  with  decinormal  KOH 
until  slightly  pink.  Multiply  the  number  of  cubic 
centimeters  of  alkali  by  1.1;  this  gives  the  Reichert- 
Meissl  number.  For  butter  this  value  should  not 
be  less  than  24.  The  experiment  may  be  repeated 
with  oleomargarine. 

(3)  Acid  number.  Mix  equal  volumes  of  alcohol 
and  ether;  add  phenolphthalein  solution,  then  a 
drop  or  more  of  decinormal  KOH  until  slightly 
pink.  Now  dissolve  a  weighed  quantity  of  butter 
(5-10  gm.)  in  some  of  the  ether-alcohol,  and  titrate 
with  decinormal  KOH  to  a  faint  pink,  which  remains 
after  mixing.  If  the  mixture  becomes  turbid  during 
titration,  warm  it  in  a  water  bath  (with  no  flame 
near  it). 

When  fats  are  decomposed  with  the  aid  of  alkali, 
soap  is  formed.  Hence  the  origin  of  the  term 
saponification.  In  the  strictest  sense,  saponifica- 
tion  means  the  action  of  an  alkali  on  an  ester,  the 
resulting  products  being  an  alcohol  and  a  salt 
of  the  acid.  Many  use  the  word  loosely  as  synony- 
mous with  hydrolysis. 

1  To  prevent  bumping. 


TRIACID  ALCOHOLS,   FATS,  AND  SOAPS        209 

Soaps  are  metallic  salts  of  the  acids  that  occur 
in  fats.  Ordinary  soaps  are  mixtures  of  potassium 
or  sodium  palmitate,  stearate,  and  oleate.  Potas- 
sium soap  is  soft  soap,  commonly  called  green  soap. 
In  many  countries  its  yellow  color  is  changed  to 
green  by  the  addition  of  indigo.  It  contains  the 
glycerol  that  is  freed  by  saponification.  Sodium 
soap  is  hard  soap,  which  has  been  freed  of  glycerol 
by  "  salting  out  "  in  the  manner  described  in  the 
experiment.  Castile  or  Venetian  soap,  if  genuine, 
is  made  from  olive  oil.  It  contains  no  free  alkali. 
It  is  slightly  yellow  in  color.  Calcium,  mercury, 
lead,  copper,  and  many  other  metals  form  insoluble 
soaps. 

Cheap  soaps  are  made  with  resin,  sodium  resinate 
acting  similarly  to  true  soap. 

The  cleansing  action  of  soap  is  largely  due  to 
hydrolytic  dissociation  of  the  salts  in  dilute  soap 
solution.  This  dissociation  can  be  demonstrated 
as  follows:  Add  phenolphthalein  to  a  concentrated 
soap  solution,  and  only  a  slight  red  appears;  now 
dilute  with  a  large  quantity  of  water,  and  a  decided 
red  develops  (for  effect  of  dilution  on  dissociation, 
see  p.  68).  The  lather  also  aids  mechanically  in 
removing  dirt.  Sodium  oleate  is  the  most  soluble 
of  the  salts  of  soap,  and  hydrolyzes  the  least.  The 
hydrolyzed  stearate  and  palmitate  furnish  colloidal 
particles.  Various  substances  adsorb  to  these  par- 
ticles, facilitating  their  removal  in  the  washing 
process.  This  explains  why  vaseline  can  be  removed 
by  first  treating  the  vaseline  with  a  fat,  and  then 
using  soap ;  the  vaseline  is  adsorbed. 


210  ORGANIC  CHEMISTRY 

The  free  alkali  of  soap  solution  probably  acts  to 
some  extent  to  saponify  the  grease  on  the  surface 
to  be  washed;  while  the  sodium  oleate  acts  to  emul- 
sify the  fat.  Saponification,  emulsification,  and 
adsorption  are  all  of  them  factors  in  the  cleansing 
process. 

Experiments.  (1)  Put  into  a  flask  about  10 
gm.  of  lard  or  tallow,  add  5  c.c.  of  60%  KOH  and 
50  c.c.  of  alcohol;  attach  an  upright  air  condenser 
tube,  and  boil  moderately.  After  boiling  half  an 
hour  test  by  shaking  a  drop  of  the  fluid  with  half 
a  test-tube  of  water;  if  no  oily  drops  separate  out, 
saponification  is  complete.  Dilute  with  50  c.c.  of 
hot  water.  While  hot  add  an  equal  volume  of 
saturated  solution  of  NaCl.  Sodium  soap  will 
separate  as  a  top  layer  and  finally  solidify. 

(2)  To  same  soap  solution  add  hydrochloric  acid. 
Free  fatty  acids  separate  and  rise  to  the  top.     Collect 
the  fatty  acids  on  a  filter,  wash  thoroughly  with 
water,   press  between  filter  paper,   and  crystallize 
from  hot  alcohol. 

(3)  Make  insoluble  soap  by  treating  same  soap 
solution   with   calcium   chloride   solution    (calcium 
soap),  with  lead  acetate  (lead  soap),  copper  sulphate, 
and    solutions    of    other    metallic    salts.     Explain 
"  hardness  "  of  water. 

In  a  soap  solution  at  least  part  of  the  soap  is  in 
the  colloidal  state;  a  concentrated  solution  made 
with  the  aid  of  heat  gelatinizes  on  cooling  (hydrogel). 
The  colloidal  behavior  of  the  solution  is  said  to 


TRIACID  ALCOHOLS,  FATS,  AND  SOAPS         211 

be  due  in  large  measure  to  hydrolytic  dissociation  of 
the  salt,  the  relatively  insoluble  product  going  into 
colloidal  solution.  Dried  soap  swells  when  soaked 
in  water. 

Lanolin  is  a  fat-like  substance  prepared  by  purify- 
ing wool  grease.  It  contains  about  25%  of  water 
and  will  take  up  more  water  until  it  holds  80%. 
It  is  more  closely  related  to  waxes  than  to  fats,  since 
by  saponification  its  esters  yield  monacid  alcohols, 
such  as  ceryl  alcohol.  In  addition  to  esters  it  con- 
tains free  acids,  free  alcohols,  cholesterol,  and 
isocholesterol. 


CHAPTER  XVI 

HYDROXY-ACIDS 

Hydroxy-acids  contain  both  alcohol  (OH)  and  acid 
(COOH)  groups.  The  acid  properties,  however,  are 
more  marked  than  the  alcohol  properties.  They 
are  not  acid  alcohols,  but  hydroxy-acids,  and  may 
therefore  be  defined  as  acids  in  which  a  hydrogen 
atom  attached  to  one  of  the  carbon  atoms  is  re- 
placed by  hydroxyl.  They  are  often  called  oxy- 
acids. 

The  simplest  possible  hydroxy-acid  would  be 
hydroxy-formic  acid, 

H- COOH ->  HO- COOH. 

(Formic  acid)      (Hydroxy-formic  acid) 

It  will  be  observed  that  this  is  identical  with  the 
hypothetical  carbonic  acid,  ^COs. 
The  lowest  typical  hydroxy-acid  is  hydroxyacetic 

/OH 

acid,  CH2<f  ^^^-r^  or  glycollic  acid  (mentioned  pre- 
\COOH 

viously  under  glycol). 

Glycollic  acid  (ethanolic  acid)  may  be  prepared  in 
many  ways,  starting  with  either  an  alcohol  or  an 
acid: 

(1)  By  oxidation  of  glycol  or  glycol  aldehyde  (see 
p.  194). 

(2)  By  forming  the  cyanogen  derivative  of  methyl 

212 


HYDROXY-ACIDS  213 

alcohol,  or,  what  is  the  same  thing,  the  cyanhydrin  of 
formaldehyde,  then  hydrolyzing: 

/H  ON 

/ 


H.CO+HCN=H.CHOH, 

(Cyanhydrin  of 
formaldehyde) 

/CN  /COOH 

CH2<       +2H20=CH2<  +NH3. 

MJxl  Mjii 

(3)  By  boiling  monochloracetic  acid  with  water  : 


OH 


CH2C1  -  COOH  +H20  =  CH2<^  +HC1. 

(4)  By  treating  aminoacetic  acid  (glycocoll)  with 
nitrous  acid: 


(Glycocoll) 

These  methods  are  in  general  applicable  to  other 
hydroxy-acids. 

Glycollic  acid  (as  also  other  hydroxy-acids)  forms 
esters   by    virtue   of   either   the   hydroxyl   or   the 
carboxyl    group;     for    example,    ethyl    glycollate,1 
OTT 

CH/—  COO-C2H5>       and       Slycollic       acetate, 
'  .OOC.CHs 


—  COOH  ' 

Glycollic  acid  is  found  in  green  grapes  and  else- 
where. It  forms  needle  crystals,  melting  at  80°. 
It  is  a  stronger  acid  than  acetic  acid.  When  heated 

Distinguish  glycollates  from  the  glycolates  derived  from 
glycol  (p.  194). 


214  ORGANIC  CHEMISTRY 

in  an  atmosphere  of  carbon  dioxide  at  210°,  it 
combines  with  itself,  losing  water,  and  thus  forms 
an  anhydride  called  glycollid: 


.2<C 


OHH10  OC 

/CH 


CH2  CH2+2H20. 

COO 

This  has  neither  alcoholic  nor  acidic  properties. 

Hydroxypropionic  acids  are  commonly  called 
lactic  acids.  Just  as  there  are  two  monochlorpro- 
pionic  acids,  a  and  /3,  so  there  are  an  a-hydroxy- 
propionic  acid  and  a  /3-hydroxypropionic  acid.  The 
j8  acid, 

/OH 
CH/--  CH2—  COOH, 

shows  by  its  reactions  that  it  is  related  to  ethylene 
(see  p.  300).  It  is  therefore  called  ethylene  lactic 
acid.  It  is  unimportant. 

Lactic  acid  proper,  a-hydroxypropionic  acid, 

/OH 
CH3-CH^--COOH, 

is  known  in  three  forms  as  isomers.  As  with  some 
of  the  amyl  alcohols  (p.  144),  these  isomers  have 
identical  structural  formulae.  Isomerism  of  the 
kind  to  be  described  now  is  called  stereoisomerism.1 
1  Stereochemistry  (stereos  meaning  solid)  treats  of  those  chem- 
ical and  physical  phenomena  that  are  supposed  to  be  caused  by 
the  relative  positions  in  space  occupied  by  the  atoms  within 
the  molecule. 


HYDROXY-ACIDS  215 

To  understand  this  it  is  necessary  to  conceive  of  the 
atoms  of  the  molecules  as  being  arranged  in  space, 
and  not  on  one  plane  as  in  ordinary  formulae.  The 
main  carbon  atom  is  thought  of  as  being  placed  in 
the  center  of  a  tetrahedron,  at  the  apex  of  each  solid 
angle  of  which  is  situated  an  atom  or  group.  Models 
of  wood  or  pasteboard  will  be  helpful  in  understand- 
ing this.  To  represent  a-lactic  acid,  -write  the  groups 
CH3,  OH,  H,  and  COOH  at  the  corners  of  the 
tetrahedron,  thus: 

OH 


CH3  COOH 

Try  the  effect  of  interchanging  these  groups  in  all 
possible  ways.  It  will  be  found  that  two  and  only 
two  different  arrangements  are  possible.1  Further, 
when  the  tetrahedron  representing  one  combination 
is  held  before  a  mirror,  the  image  in  the  mirror  will 
be  seen  to  correspond  exactly  to  the  other  possible 
arrangement.  This  is  true  only  in  the  case  of  com- 
pounds that  would  be  represented  as  having  four 
different  groups  at  the  corners.  If*  two  of  these 

1  The  truth  of  this  statement  can  be  most  clearly  shown 
by  writing  down  the  various  possible  arrangements  and  then 
marking  off  those  that  are  identical.  The  student  will  be 
interested  in  observing  that  his  hands  are  mirror  images  of  each 
other. 


216  ORGANIC  CHEMISTRY 

groups   are   the   same,    only   one    arrangement   is 
possible  and  stereoisomerism  cannot  occur. 

The  tetrahedron  representing  lactic  acid  is  unsym- 
metrical  as  regards  the  kind  of  groups  present;  its 
central  carbon  atom  is  therefore  said  to  be  an  asym- 
metric carbon  atom.  It  has  been  found  that  com- 
pounds containing  an  asymmetric  carbon  atom 
rotate  the  plane  of  polarized  light.1  Dextrolactic 
acid  rotates  it  to  the  right,  laevolactic  acid  rotates 
it  to  the  left.  As  represented  by  models,  laevolactic 
acid  is  the  mirror-image  of  dextrolactic  acid.  Ordi- 
nary lactic  is  also  an  a-lactic  acid,  but  it  does  not 
affect  polarized  light;  it  is  optically  inactive.  It  has 
been  shown  to  consist  of  equal  quantities  of  dex- 
trolactic and  Isevolactic  acid  molecules;  such  a 
substance  is  called  racemic.2  The  two  constituent 
acids  of  racemic  acid  neutralize  each  other  in  their 
action  on  polarized  light.  Optically  active  substances 
that  have  a  physiological  action  may  show  a  dif- 
ferent degree  of  action  on  the  animal  organism 

*A  few  optically  active  organic  compounds  have  been  pre- 
pared which  contain  asymmetric  atoms  other  than  carbon. 
Certain  quaternary  bases  have  an  asymmetric  N  atom,  as 

C,Hs\ 
\ 
C6H5.CH2-N 


The  pentavalent  N  atom  has  been  conceived  of  as  at  the  center 
of  a  pyramid. 

2  Racemic  substances  are  not  always  mixtures;  thed,  ^-mixtures 
might  better  be  called  conglomerates.  The  racemic,  properly 
speaking,  contain  the  two  active  molecules  in  some  sort  of 
molecular  combination  (cf.  tartaric  acid). 


HYDROXY-ACIDS  217 

according  to  whether  it  is  the  d  or  I  isomer  that  is 
acting  (see  nicotine,  p.  430,  atropine,  p.  432,  and 
cocaine,  p.  433). 

Dextrolactic  acid  (d-lactic  acid)  is  also  called 
sarcolactic  acid,  because  it  occurs  in  flesh.  It  is 
present  in  beef  extract.  It  is  also  the  product  of 
fermentation  of  dextrose  by  the  Micrococcus  acidi 
paralactici.  Its  salts  are  laevorotatory. 

Laevolactic  acid  (/-lactic  acid)  is  obtainable  by  fer- 
mentation of  dextrose  by  the  Micrococcus  acidi  Icevo- 
lactici. 
f    Racemic  lactic  acid  (d-,  Mactic  acid)  is  a  syrupy 

15° 
liquid  having  a  specific  gravity  of  1.2485  at  -^-. 

It  is  stronger  than  most  organic  acids,  and  much 
stronger  than  propionic  and  ethylene  lactic  acids, 
to  which  it  is  related.  It  is  the  product  of  ordinary 
lactic  acid  fermentation.  When  milk  sours,  milk- 
sugar  becomes  converted  into  lactic  acid  by  micro- 
organisms : 


=4C3H6O3. 

(Lactose)  (Lactic  acid) 

No  matter  in  what  way  lactic  acid  is  artificially 
produced  by  synthesis,  the  synthetic  acid  is  always 
racemic.  The  law  of  probability  as  applied  to 
chemical  synthesis  calls  for  the  formation  of  just 
as  many  molecules  having  the  dextro-arrangement 
as  the  laevo.  It  can  be  shown  that  d}  Mac  tic  acid 
contains  dextrolactic  acid  by  growing  the  mold 
Penicillium  glaucum  in  a  solution  of  d,  /-ammonium 
lactate,  because  the  mold  destroys  the  Isevolactic 


218  ORGANIC  CHEMISTRY 

acid.  On  the  other  hand  it  may  be  shown  to  con- 
tain Isevolactic  acid  by  fractional  crystallization  of 
a  solution  of  strychnine  lactate,  since  the  Isevo- 
lactate  crystals  are  formed  first. 

When  heated  to  150°  in  dry  air,  lactic  acid  changes 
to  an  anhydride  called  lactid  (cf.  glycollic  acid,  p. 
214).  Hydriodic  acid  reduces  lactic  acid  to  pro- 
pionic  acid  (see  p.  185). 

EXPERIMENT.  In  a  retort  mix  5  c.c.  of  lactic 
acid,  10  c.c.  of  water,  and  5  c.c.  of  concentrated 
H^SO*.  Connect  with  a  condenser.  Heat  with  a 
smoky  flame.  Test  the  distillate  for  aldehyde 
(see  p.  153)  and  for  formic  acid  (see  p.  160) : 

CH3  •  CHOH  •  GOOH  =  CH3  •  CHO  +H  •  COOH. 
/3-Hydroxybutyric    acid  (/3-oxybutyric  acid), 
CH3  -  CH(OH)  •  CH2  •  COOH, 

is  pathologically  of  importance,  since  it  may  occur  in 
the  blood  or  urine,  especially  in  diabetes.  It  is 
laevorotatory,  its  specific  rotation  (p.  245)  being 
-24.12°. 

It  will  be  noticed  that  the  ketone  acid  acetoacetic 
acid  (/3-ketobutyric  acid)  corresponds  to  the  above 
alcohol  acids,  just  as  ketones  correspond  to  second- 
ary alcohols  (see  also  p.  192) : 

CH3  •  CHOH  -CH2-  COOH  (cf.  CH3  •  CHOH  -  CH3) 
CH3.CO-CH2-COOH  (cf.  CH3-CO-CH3). 

/3-Hydroxybutyric  acid  can  be  readily  oxidized  to 
acetoacetic  acid  by  hydrogen  peroxide. 


HYDROXY-ACIDS  219 

T-Hydroxy-acids  are  very  unstable.  They  readily 
split  off  water  to  form  anhydrides  called  lactones, 
thus: 

CH2  (OH)  •  CH2  •  CH2  •  COOH 

(7-Hydroxybutyric  acid) 


o- 

(Butyrolactone) 

The  carbon  chain  is  closed  by  a  linking  through 
oxygen.  It  is,  however,  not  a  typical  closed  chain. 
The  presence  of  hydrogen  ions  acts  catalytically 
to  hasten  the  formation  of  the  lactone,  and  it  is 
supposed  that  the  H  ions  of  the  7-hydroxy  acid  itself 
have  this  action,  causing  autocatalysis.  When  boiled 
with  caustic  alkalies,  the  lactones  form  salts  of  the 
corresponding  hydroxy-acids;  thus  lactones  give 
a  "  saponification  value."  This  fact  must  be 
borne  in  mind  in  examining  unknown  substances 
supposed  to  be  fats  or  waxes. 

Dihydroxymonobasic  acids  are  illustrated  by  glyceric 
acid, 

CH2OH 
CHOH. 


COOH. 


Glyoxylic  acid,  which  has  been  previously  men- 
tioned (p.  194),  while  classed  as  an  aldehydic  acid, 
is  according  to  some  chemists  a  dihydroxy-acid, 
because  it  holds  a  molecule  of  water  inseparable 
from  it  (cf.  chloral  hydrate): 


220  ORGANIC  CHEMISTRY 

/H 
COOH  •  C\     +HOH  =  COOH 

%0  OH 

or 

CH(OH)2-COOH. 

It  is  a  reducing  agent  like  aldehydes  (as  chloral 
hydrate). 

EXPERIMENTS.  (1)  To  20  c.c.  of  a  strong  solu- 
tion of  oxalic  acid  add  1  gm.  sodium  amalgam; 
when  evolution  of  gas  has  ceased,  filter.  The 
filtrate  is  a  dilute  solution  of  glyoxylic  acid: 

COOH  COOH 

-  +H20. 


COOH  CHO 

(Oxalic  acid)     (Nascent  (Glyoxylic  acid) 

hydrogen) 

(2)  To  5  c.c.  of  albumin  solution  (egg-white 
solution)  add  5  c.c.  of  the  glyoxylic  acid  solution, 
then  5  c.c.  of  concentrated  H2S04;  mix  and  heat 
gradually;  a  bluish-violet  color  is  obtained,  due 
to  trytophan  contained  in  the  protein  molecule. 
Most  proteins  give  this  test. 

An  example  of  a  trihydroxy-acid  is  cholic  or 
cholalic  acid,  (CH2OH)2  [C20H31(CHOH)]  COOH. 
The  constitution  of  the  C2oHsi  portion  of  the 
formula  is  unknown.  This  acid  is  important  phys- 
iologically, since  its  combinations  with  glycin  and 
with  taurin,  glycocholic  and  taurocholic  acids,  are 
the  most  valuable  constituents  of  bile. 

Glycocholic  acid  has  the  formula: 

C20H3i(CHOH)  (CH2OH)2  -  CO—  HN  -  CH2COOH. 


HYDROXY-ACIDS  221 

Taurocholic  acid  is 
[C20H3i(CHOH)  (CH2OH)2CO— NH-  (CH2)2S03H. 

Glycuronic  acid  is  an  aldehydic  tetrahydroxy-acid, 
CHO-(CHOH)4-COOH,  the  arrangement  of  the 
secondary  alcohol  groups  being  the  same  as  in 
dextrose.  It  is  formed  by  the  animal  body  from 
dextrose  when  it  is  needed  to  combine  with  abnormal 
substances,  such  as  drugs  or  indol.  It  is  excreted 
in  the  urine  as  paired  glycuronates;  these  are 
Isevorotatory.  By  heating  with  dilute  acid,  gly- 
curonic  acid  is  set  free;  this  is  dextrorotatory.  It 
is  closely  related  to  monosaccharides,  differing  only 
in  the  change  of  the  CH2OH  group  to  COOH. 
The  free  acid  and  some  of  its  combinations  reduce 
alkaline  copper  solutions  (like  other  aldehydes), 
more  particularly  after  prolonged  heating  of  the 
mixture;  so  that  occasionally  a  mistake  may  be  made 
in  concluding  that  a  reducing  urine  contains  sugar. 
It  is  not  fermentable.  It  gives  the  pentose  reactions 
(see  p.  230). 

Monohydroxydibasic  Acids. 
COOH 

Tartronic  acid,    CHOH,  has  been  supposed  to  take 

I 
COOH 

part  in  the  physiological   synthesis   of  uric   acid, 
particularly  in  birds  (see  p.  290). 
Malic  acid  is  hydroxysuccinic  acid, 
CH(OH)— COOH 


222  ORGANIC  CHEMISTRY 

It  is  contained  in  sour  fruits,  e.g.,  apples  and 
cherries. 

Agaric  Acid  is  used  as  a  remedy.  Its  formula  is 
Ci4H27(OH)(COOH)2. 

Dihydroxydibasic  Acids. 

COOH 
|     OH 

Mesoxalic   acid,   C\       ,  is  the  third  exception  to 
|XOH 
COOH 

the  rule  that  two  hydroxyls  cannot  be  attached  to 
the  same  carbon  atom,   chloral  hydrate  and  gly- 
oxylic  acid  being  the  two  other  exceptions. 
Tartaric  acid  is  dihydroxysuccinic  acid, 

CH(OH)— COOH 
CH(OH)— COOH* 

Here  there  are  two  asymmetric  carbon  atoms  (see 
p.  216)  in  the  molecule.  This  fact  causes  a  species 
of  stereoisomerism,  that  is  more  difficult  to  under- 
stand than  that  of  lactic  acid.  With  the  aid  of 
models  it  can  be  clearly  understood.  Arrange  pairs 
of  tetrahedra  as  shown  in  the  diagram. 

It  will  be  noticed  in  the  case  of  dextro-  and  Icevo- 
tartaric  acids  that  the  groups,  OH  and  OH,  H  and  H, 
are  connected  by  straight  lines  and  are  on  opposite 
sides  of  a  line  connecting  the  centers  of  the  tetra- 
hedra; they  are  diagonally  opposite,  while  the  COOH 
groups  are  vertically  opposite  each  other,  both 
being  at  an  angle  of  the  tetrahedron  that  points  for- 


HYDROXY-ACIDS 


223 


ward.  As  with  the  models  for  lactic  acid,  these 
models  for  active  tartaric  acids  cannot  be  made 
identical  by  turning  the  model  about. 

Place  the  Ia3votartaric  model  before  a  mirror;  the 
image  corresponds  to  dextrotartaric  acid. 

Racemic  tartaric  acid  when  in  solution  is  a  mixture 
of  equal  quantities  of  dextro-  and  Ia3vo-tartaric  acids 
(cf.  racemic  lactic  acid).1  There  is,  however,  an- 
other inactive  tartaric  acid  which  cannot  be  sepa- 


Dextro-tartaric  acid. 


Laevo-tartaric  acid. 

FIG.  22. 


Meso-tartaric  acid 


rated  into  optically  active  acids.  This  is  mesotartaric 
acid.  By  studying  the  diagram  above,  or  a  model, 
it  will  be  seen  that  the  neutralization  of  optical 
properties  is  an  inner  molecular  one,  since  the 
arrangement  of  the  groups  on  the  top  corresponds 
to  that  of  Isevotartaric  acid,  while  the  arrangement 
at  the  base  corresponds  to  that  of  dextrotartaric.2 

1  The  racemic  tartaric  acid  crystals,  however,  are  represented 
by  the  formula  4C4H606 +2H2O. 

2  It  will  further  be  noted  that  an  acid  of  this  variety  is  not 
possible  in  the  case  of  lactic  acid. 


224 


ORGANIC  CHEMISTRY 


Racemic  and  mesotartaric  acids  differ  widely  in 
melting-point  and  solubility. 

Ordinary  tartaric  acid  is  dextrorotatory.  It  is 
contained  in  grape-juice  as  potassium  bitartrate  or 
acid  tartrate,  HOOC(CHOH)2COOK.  When  wine 
is  produced  this  salt  separates  out  because  of  its 
relative  insolubility  in  dilute  alcohol.  This  crude 
tartar,  or  argol,  is  called  cream  of  tartar  when  puri- 
fied. It  is  used  in  the  manufacture  of  the  best 
baking-powders.  Baking-powder  is  a  mixture  of 
sodium  bicarbonate  and  some  acid  salt,  which  on 


FIG.  23. 

being  dissolved  liberates  carbon  dioxide  from  the 
bicarbonate.  Tartaric  acid  is  obtained  from  potas- 
sium bitartrate  by  precipitation  as  calcium  tartrate, 
from  which  the  acid  is  liberated  by  using  the  proper 
amount  of  dilute  sulphuric  acid.  It  forms  large 
crystals,  melting  at  170°.  On  heating  further  it 
turns  brown  and  gives  off  an  odor  like  caramel. 
It  is  easy  soluble. 

Dextrotartaric  acid  can  be  converted  into  racemic 
acid  by  boiling  with  an  excess  of  strong  sodium 
hydroxide  solution.  The  two  methods  given  for 
separating  racemic  lactic  acid  into  the  active  acids 


HYDROXY-ACIDS  225 

are  applicable  also  to  racemic  tartaric  acid.  Pasteur 
discovered  a  third  method  which  is  very  interesting. 
By  slow  evaporation  (below  28°)  of  a  solution  of 
sodium  ammonium  racemate,  two  classes  of  crystals 
can  be  obtained,  which  from  their  appearance  might 
be  called  right-handed  and  left-handed  crystals 
(see  Fig.  23). 

The  crystals  are  mirror-images  of  one  another. 
These  can  be  picked  out  mechanically;  one  set 
furnishes  dextrotartaric  acid,  the  other  Isevotartaric 
acid. 

Rochelle  salt  is  sodium  potassium  tartrate, 

CH(OH)— COONa 
|  +4H20. 

CH(OH)— COOK 

This  has  the  power  of  holding  Cu(OH)2  in  solu- 
tion, as  in  Fehling's  solution.  It  is  used  as  a 
cathartic. 

Tartar  emetic  is  potassium  antimonyl  tartrate, 

CH(OH)— COOK 
CH(OH)— COO(SbO). 

It  is  used  as  a  medicine. 

EXPERIMENTS.  (1)  Heat  some  tartaric  acid  in  a 
test-tube,  stirring  it  with  a  thermometer.  Note 
the  melting-point.  Remove  the  thermometer  and 
continue  heating.  The  acid  turns  brown  and  emits 
an  odor  like  scorched  sugar.1 

1  Certain  other  acids  act  in  the  same  way,  particularly 
citric,  malic,'  tannic,  and  gallic. 


226  ORGANIC  CHEMISTRY 

(2)  Prepare   tartar   emetic.     Dissolve   5   gm.   of 
potassium  acid  tartrate  in  50  c.c.  of  water,  add 
4  gm.  Sb20s  and  boil.     Filter  and  test  some  of  the 
filtrate  for  antimony  with  H2S.     Set  aside  the  rest 
of  the  filtrate  to  secure  crystals  by  slow  evaporation. 

(3)  After  reading  a  description  of  the  polariscope  1 
and  its  manipulation,  determine  the  rotary  power  of 
a  strong  solution  of  tartaric  acid. 

Monohydroxytribasic  Acids. 

CH2— COOH 

I 
Citric  Acid,  C(OH) — COOH,  is  present  in  currants, 

CH2— COOH 

gooseberries,  and  lemons.  It  forms  large  crystals 
(having  one  molecule  of  water  of  crystallization) 
and  is  easily  soluble.  Citrates  are  valuable  medi- 
cines. Citrates  redissolve  Cu(OH)2  which  has 
been  precipitated  by  NaOH  (cf.  Rochelle  salt  in 
Fehling's  solution). 

Other  hydroxyacids  that  are  mentioned  else- 
where are  dihydroxystearic  acid  (p.  207)  and  ricino- 
leic  acid  (p.  304). 

1 A  good  description  can  be  found  in  Cohen's  Practical 
Organic  Chemistry,  also  in  Mathews'  Physiological  Chemistry. 


CHAPTER  XVII 

CARBOHYDRATES-  AND  GLUCOSIDES 

CARBOHYDRATES 

THIS  class  of  compounds  is  of  very  great  im- 
portance, since  it  includes  sugars  and  starches. 
The  name  carbo(n)hydrates  calls  attention  to  the 
fact  that  the  hydrogen  and  oxygen  in  their  for- 
mulae have  the  same  ratio  as  in  the  formula  for 
water;1  therefore  a  general  formula  often  given 
for  carbohydrates  is  Cn(H20)m. 

This,  however,  is  misleading,  for  there 'are  a  num- 
ber of  non-carbohydrate  substances  that  conform 
to  this  formula,  such  as  acetic  acid,  C2H402,  and 
lactic  acid,  CaHeOs. 

Carbohydrates  may  be  defined  as  including  mono- 
saccharides  and  those  more  complex  substances 
that  yield  by  hydrolysis  simply  monosaccharides. 

All  monosaccharides  contain  in  their  formulae  a 
CO  group,  either  in  an  aldehyde  group  or  as  the 
ketone  group,  and  have  also  an  alcoholic  hydroxyl 
attached  to  each  of  the  other  carbon  atoms.  This 
may  be  condensed  to  the  statement:  mono- 
saccharides are  aldehyde  or  ketone  derivatives  of 
polyhydroxylic  alcohols. 

There  are  four  classes  of  carbohydrates,  namely, 

1  It  should  be  pointed  out  in  this  connection  that  the  term 
hydrate  as  applied  to  alkalies  is  inaccurate,  e.g.,  NaOH  is  so- 
dium hydroxide,  not  a  hydrate. 

227 


228  ORGANIC  CHEMISTRY 

monosaccharides,  disaccharides,  trisaccharides  and 
poly  saccharifies.1  Monosaccharides  are  the  simplest 
carbohydrates.  From  the  linking  of  fcwo  monosac- 
charide  molecules,  disaccharides  result.  A  trisac- 
charide  contains  in  its  molecule  three  monosac- 
charide  molecules.  Polysaccharides  have  complex 
molecules  that  can  be  resolved  into  many  mono- 
saccharide  molecules.  Monosaccharides  and  disac- 
charides act  as  very  weak  acids,  but  their  H  ion 
concentrations  are  extremely  low. 

MONOSACCHARIDES 

According  to  the  number  of  carbon  atoms  present, 
monosaccharides  are  called  dioses,  trioses,  tetrpses, 
pentoses,  hexoses,  heptoses,  octoses,  and  nonoses. 

Aldoses  are  those  containing  an  aldehyde  group, 
while  ketoses  are  those  having  a  ketone  group. 

CH2OH 

GlycoLaldehyde,  I  ,  may  be  considered  a  diose. 

CHO 

Glycerose  can  be  obtained  by  mild  oxidation  of 
glycerol  (or  lead  glycerate);  it  is  a  mixture  of  an 
aldehyde  and  a  ketone,  and  since  each  contains  three 
carbon  atoms,  they  are  trioses: 

CH2OH          CH2OH          CH2OH 

CHOH    ->    CHOH    +    CO 
CH2pH          CHO  CH2OH 

(Glycerol)         (Glyceric  aldehyde)      (Dihydroxyacetone) 
(Glycerose) 

1  These  are  also  called  monosaccharoses,  disaccharoses,  tri- 
saccharoses,  and  polysaccharoses. 


CARBOHYDRATES  AND  GLUCOSIDES  229 

CH2OH 

CHOH 

Tetrose,    |          ,  can  be  obtained  by  polymeriza- 
CHOH 


CHO 


tion   of   glycol  aldehyde.      A   ketose  tetrose   also 
occurs. 

The  chief  pentoses  are  d-arabinose  and  [Z-xylose. 
The  following  formulae  represent  their  isomeric  rela- 
tion: 

CH2OH  CH2OH 

HO— C— H  HO— C— H 

I  I 

HO— C— H  H— C— OH 

H— C— OH         HO— C— H 

I  I 

CHO  CHO 

(d-arabinose)  (Z-xylose) 

Arabinose  is  obtainable  by  boiling  gum-arabic  with 
dilute  acid.  Xylose  can  be  obtained  by  similar 
means  from  bran  or  wood.  Racemic  arabinose  is 
sometimes  present  in  the  urine  as  an  abnormal 
constituent.  Several  ketose  pentoses  are  known. 

On  account  of  having  three  asymmetric  C  atoms, 
four  main  arrangements  and  the  mirror  images  of 
these  are  possible,  so  that  eight  aldose  pentoses 
are  obtainable.  Seven  of  these  are  known  at 
present. 

Both  arabinose  and  xylose  reduce  Fehling's  solu- 
tion and  form  osazones  with  phenylhydrazine  (the 


230  ORGANIC  CHEMISTRY 

nature  of  the  osazone  reaction  will  be  explained 
presently).  Neither  is  fermented  by  pure  yeast. 
They  give  certain  color  reactions,  which  will  be 
illustrated  in  the  experiment  below. 

If  a  pentose  is  boiled  with  strong  HC1,  an  aldehyde 
having  a  closed  chain  (furfurol)  is  produced : 


HOjCH— GHJOHJ 

TT-PTT      P/S     I 

O^M    <-\|OH|.CHO=CH    C-CHO+3H20 

N0|H  \   ./ 

(P^ntoaer""  f{    ' 

(Furfurol) 


Most  of  the  monosaccharides  thus  far  considered 
have  not  been  found  in  natural  products. 

Several  methyl  derivatives  of  monosaccharides 
occur  in  glucosides,  as  digitoxose,  CeH^O^  a  di- 
methyltetrose,  digitalose,  CyHuOs,  a  dimethyl- 
pentose,  and  rhamnose,  C6Hi205,  a  methyl  pen- 
tose. 

EXPERIMENT.  Pentose  test.  To  2  c.c.  of  water  in 
a  test-tube  add  2  c.c.  of  HC1  and  warm.  Add 
phloroglucin,  a  little  at  a  time,  as  long  as  it  dissolves. 
Now  add  1  c.c.  of  arabinose  solution,  and  heat  until 
a  red  color  is  obtained;  examine  at  once  with  a 
small  spectroscope,  when  an  absorption  band 
between  the  d  and  e  lines  will  be  seen.  Heat  until 
a  precipitate  forms,  add  some  amyl  alcohol,  and 
shake;  the  alcohol  becomes  colored  and  gives  the 
same  spectroscopic  appearance  as  above. 


CARBOHYDRATES  AND  GLUCOSIDES 


231 


The  hexoses  are  the  sugars  of  prime  impor- 
tance. The  chief  ones  are  dextrose,  galactose,  and 
laevulose;  the  first  two  are  aldoses,  while  the  last 
is  a  ketose: 


CH2OH 

1 

CH2OH 

1 

CH2OH 

1 

HO—  C—  H 

1 

HO—  C—  H 

1 

HO—  C—  H 

1 

HO—  C—  H 

H—  C—  OH 

HO—  C—  H 

H—  C—  OH 

H—  C—  OH 

H—  C—  OH 

HO— C— H 
CHO 

Dextrose  (d-glucose)  ) 


HO— C— H 
CHO 

(d-galactose) 


i, 


)H2OH 

(Lsevulose  (cMructose)) 


The  aldoses  have  four  asymmetric  C  atoms,  there- 
fore eight  main  arrangements  of  the  secondary  alco- 
hol groups  together  with  their  mirror  images  make 
sixteen  aldose  hexoses  possible.  Twelve  of  these 
have  been  studied. 

d-Mannose  differs  from  d-glucose  only  in  the 
arrangement  of  the  fourth  secondary  alcohol  group. 
The  mirror  image  aldoses  are  the  Z-hexoses  and  are 
Isevorotatory.  The  chemical  name  for  laevulose 
is  fructose,  and  it  is  called  d-fructose  because  the 
arrangement  of  its  secondary  alcohol  groups  is  the 
same  as  in  d-glucose. 

Six  ketose  hexoses  are  known,  the  only  one  of 
importance  being  Isevulose.  Two  methyl  hexoses 
have  been  prepared. 

Condensation  of  the  aldehyde  and  ketone  trioses 


232  ORGANIC  CHEMISTRY 

in  glycerose  results  in  the  production  of  a  ketose, 
d,  I  fructose,  thus  : 

CH2OH  CH2OH 

CHOH  CHOH 

CHO+HCHOH   =  CHOH 

CO        CHOH 

I          I 
CH2OH     CO 

(Glyceric  aldehyde)      (Dihydroxyacetone) 

(Glycerose)  CH2OH 

(Ketohexose) 

The  condensation  of  formaldehyde  induced  by 
weak  alkali  yields  the  same  product. 

All  the  synthetic  sugars  are  optically  inactive 
when  produced  by  purely  chemical  means. 

Physiologists  believe  that  in  the  animal  body 
glycerol  (from  fat)  may  be  converted  into  a  hexose, 
at  least  under  certain  circumstances. 

Dextrose  is  the  aldehyde  of  the  hexacid  alcohol  sor- 
CH2OH 


toly  (CHOH)  4,  and  can  be  converted  into  the  latter 

CH2OH 

by  reduction.    Dextrose   can  be   oxidized   to  the 

COOH 

dibasic  acid  saccharic  acid,  (CHOH)  4.    The  alcohol 


C 


OOH 

dulcitol,  a  stereoisomer  of  sorbitol,  can  be  oxidized 
to  galactose,  and  this  aldehyde  rApnosaccharide  can 


CARBOHYDRATES  AND  GLUCOSIDES  233 

COOH 

I 
be  oxidized  further  to  mucic  acid,  (CHOH)4.    Sim- 

COOH 

ilarly  there  are  alcohols  and  acids  corresponding 
to  the  other  hexoses. 

These  alcohols  and  acids  have  the  same  arrange- 
ment of  the  secondary  alcohol  groups  as  the  mono- 
saccharides  to  which  they  are  related. 

Glycuronic  acid  (p.  221)  is  a  monobasic  acid, 
having  the  same  arrangement  of  the  CHOH 
groups  as  d-glucose,  the  aldehyde  group  also  being 
present. 

There  are  certain  proteins  that  contain  a  carbo- 
hydrate derivative  combined  with  the  protein  mole- 
cule proper;  such  are  called  glucoproteins.  This 
combined  sugar  has  been  found  in  most  cases  to 

CH2OH 

(CHOH)3 

be  an  aminohexose,  generally  glucosamine,    \  , 

CHNH2 

CHO 

sometimes  galactosamine.  Z-Xylose  is  found  in 
combination  in  nucleoproteins.  The  sugar  group 
in  protein  may  be  detected  by  certain  color  reactions 
(see  exp.  below). 

The  question  of  the  possibility  of  the  formation  of  dex- 
trose from  proteins  other  than  glucoproteins  is  of  very  great 
physiological  importance.  The  chemistry  of  the  problem  will 
now  be  briefly  considered.  Proteins  readily  split  up  into  amino- 
acids  (see  p.  267).  When  we  reason  on  purely  chemical  grounds, 


234  ORGANIC  CHEMISTRY 

we  see  that  it  is  possible  that  amino-acids  containing  three  or 
six  carbon  atoms  can  be  converted  into  dextrose. 

Alanin  can  be  changed  to  lactic  acid,  the  latter  to  glyceric 
acid,  which  can  be  reduced  to  glyceric  aldehyde,  and  finally 
this  can  be  converted  into  a  dextrose-like  sugar  by  aldol  con- 
densation. Such  a  synthesis  when  carried  out  in  the  animal 
organism  would  undoubtedly  result  in  production  of  dextrose, 
i.e.,  dextrorotatory  glucose.  It  is  quite  likely  that  serin  is  also 
convertible  into  lactic  acid  and  therefore  into  dextrose; 

CH2OH-CHNH2    •  COOH,  serin. 
CH3       .CHNH2    -COOH,  alanin. 

CH3       •  CHOH     •  COOH,  lactic  acid. 
CH2OH  •  CHOH     •  COOH,  glyceric  acid. 
CH2OH  •  CHOH     .  CHO,     glyceric  aldehyde. 
CH2OH  •  (CHOH),  •  CHO,    dextrose-like  aldose. 

The  production  of  dextrose  from  alanin,  glycocoll,  aspartic 
acid  and  glutaminic  acid  in  the  animal  body  has  been  exper- 
imentally demonstrated,  lactic  acid  being  noted  as  an  inter- 
mediate product. 

EXPERIMENT.  To  1  c.c.  of  a  strong  solution  of 
egg  protein  add  a  drop  of  saturated  solution  of 
a-naphthol  in  alcohol  (acetone-free);  then  with  a 
pipette  add  1  c.c.  of  C.P.  EbSO^  so  that  the  acid 
does  not  mix,  but  forms  a  bottom  layer.  The 
greenish  color  at  the  zone  of  contact  is  due  to  the 
reagents ;  let  the  tube  stand  until  a  violet  ring  forms. 
If  the  violet  color  does  not  appear,  tap  the  tube  so 
as  to  cause  a  slight  mixing  of  the  two  layers.  This 
is  Molisch's  test  and  is  given  by  all  carbohydrate- 
containing  substances. 


CARBOHYDRATES  AND  GLUCOSIDES  235 

Instead  of  the  alcoholic  solution  a  10%  solution 
of  a-naphthol  in  chloroform  may  be  used. 

General  Reactions  of  Monosaccharides.  They  all 
reduce  alkaline  silver,  .copper,  and  bismuth  solu- 
tions, as  do  other  aldehydes  and  some  ketones  (see 
p.  153).  All  form  osazone  crystals  when  treated 
with  phenylhydrazine  acetate  (see  exp.  below). 
The  reaction  occurs  in  two  stages;  first  the  O  of  CO 
is  substituted  (as  in  hydrazones),  then  secondly  the 
excess  of  phenylhydrazine  removes  two  H  atoms  of 
the  neighboring  CHOH  group,  converting  it  to  CO, 
and  the  latter  reacts  with  phenylhydrazine.  The 
osazone  from  Isevulose  is  identical  chemically  with 
that  from  dextrose,  because  Isevulose  has  the  same 
arrangement  of  CHOH  groups  as  dextrose,  and  the 
end  CH2OH  is  changed  to  CO  in  this  case.  In 
similar  manner  d-mannose  gives  an  osazone  that  is 
the  same  as  glucosazone, 

Methylphenylhydrazine  gives  osazones  with  ke- 
toses  only,  and  can  therefore  be  used  to  detect 
the  presence  of  Isevulose.  Glucosazone  has  the 
formula, 

CH2OH 
(CHOH)  3 
C—N-NH-CeHs. 
C=N-NH-C6H5 


236  ORGANIC  CHEMISTRY 

This  can  be  converted  by  treatment  with  warm 

CH2OH 

(CHOH)3 

hydrochloric  acid  into  glucosone,     |  When 

CO 

CHO 

glucosone  is  treated  with  nascent  hydrogen  (as  by 
using  zinc  dust),  fructose  is  formed.  Thus  we  can 
convert  an  aldose  into  a  ketose. 

Dextrose  and  galactoseare  dextrorotatory;  Isevu- 
lose  is  Isevorotatory.  They  all  have  a  different  rotary 
power  when  freshly  dissolved  from  that  which 
they  show  after  allowing  the  solution  to  stand.  This 
phenomenon  is  called  mutarotation  or  multirotation. 

This  has  been  explained  by  supposing  a  lactone-like 
linking  in  the  sugar  molecule  so  that  the  C  of  the  alde- 
hyde group  comes  to  hold  H  and  OH.  This  C  atom  is 
now  asymmetric  and  two  stereoisomers  become  possi- 
ble, designated  as  a  and  /3.  This  has  been  investi- 
gated in  the  case  of  Z-arabinose,  d-galactose,  lactose 
and  d-glucose.  This  will  be  illustrated  by  d-glucose: 
CH2OH  CH2OH 

HO— C— H  HO— C— H 

-C— H 
H— C— OH 
H 


J.J.  V_X  ^ 

HO— C— ] 


H— C— OH  HO— C— H 

a-d-glucose  /3-d-glucose 


CARBOHYDRATES  AND  GLUCOSIDES  237 

The  a  variety,  immediately  after  preparing  a 
solution,  has  a  specific  rotation  (p.  245)  of  110°, 
the  |8  variety  19°.  On  standing  each  solution 
changes  and  both  finally  come  to  a  specific  rotation 
of  52.5°;  in  the  one  solution  a  partly  changes  to 
j8,  and  in  the  other  solution  /?  partly  changes  to  a. 
The  two  come  into  equilibrium  when  40%  of  the 
glucose  is  a  and  60%  0  in  the  case  of  concentrated 
solutions.  The  change  from  the  one  form  of  glucose 
to  the  other  is  believed  to  take  place  through  an 
intermediate  form,  this  being  not  a  lactone  but 
the  hydrated  aldehyde,  CH2OH(CHOH)4CH(OH)2. 
There  is  supposed  to  be  a  trace  of  this  present  in  the 
equilibrium  mixture,  thus  explaining  the  response  of 
the  sugar  solution  to  aldehyde  tests.  Maltose  is 
believed  to  be  made  up  of  two  a-d-glucose  molecules, 
and  isomaltose  of  two  0-d-glucose  molecules. 

These  hexoses  are  fermented  by  yeast,  the  main 
products  being  alcohol  and  carbon  dioxide.  /-Glu- 
cose does  not  ferment,  possibly  because  the  optically 
active  enzyme  fits  only  the  rf-form. 

In  making  a  test  for  reducing  sugar  (dextrose,  Isevulose, 
pentoee,  or  lactose)  in  the  urine,  reduction  of  Fehling's  solution  is 
not  sufficient,  for  the  urine  may  reduce  this  reagent  slightly 
after  the  administration  of  chloral  hydrate,  camphor,  menthol, 
thymol  or  antipyrin  because  these  bodies  are  excreted  in  gly- 
curonic  acid  combination  (see  p.  221).  While  the  bismuth 
test  excludes  many  non-saccharine  substances  (uric  acid  and 
creatinin)  that  reduce  Fehling's  solution,  it  may  yet  be  positive 
with  urine  after  the  administration  of  antipyrin,  salol,  tur- 
pentine, kairin,  senna,  rhubarb,  benzosol,  sulphonal,  or  trional. 
The  phenylhydrazine  test  is  the  most  delicate  and  the  most 
positive.  The  fermentation  test,  if  positive,  is  generally  con- 


238  ORGANIC  CHEMISTRY 

elusive.  If  lactose  or  a  pentose  alone  be  present,  fermentation 
will  not  occur.  These  can  be  distinguished  by  a  special  pentose 
test,  and  in  the  case  of  lactose  by  increase  in  dextrotation  after 
boiling  with  dilute  HC1  (hydrolysis). 

Lsevulose  can  be  differentiated  from  dextrose  by  the  special 
ketose  test  and  by  laevorotation.  Chloroform  added  to  urine 
as  a  preservative  gives  reduction  because  heating  it  with  alkali 
produces  formic  acid. 

Normal  urine  has  a  reducing  power  equivalent  to 
0.2%  dextrose,  but  less  than  one-fifth  of  this  is  due 
to  dextrose. 

Dextrose  (glucose,  grape  sugar)  is  present  in  many 
fruits  and  plants,  in  honey,  and  in  the  urine  of 
diabetic  patients.  Commercial  glucose  is  made  by 
boiling  starch  with  dilute  acid;  it  is  used  for  making 
candies,  cheap  syrup,  etc.  This  crude  glucose  con- 
tains dextrin.  Pure  glucose  is  crystalline ;  if  crystal- 
lized from  water  it  contains  a  molecule  of  water  of 
crystallization,  but  if  crystallized  from  methyl  alcohol 
it  is  anhydrous.  It  is  not  so  sweet  as  cane  sugar. 

Galactose  is  obtained  from  lactose,  by  hydrolysis 
of  the  latter.  It  ferments  slowly. 

Laevulose  (fructose,  fruit  sugar)  is  contained  in 
many  sweet  fruits,  in  honey,  and  rarely  in  urine. 
It  is  difficult  to  crystallize.  Its  rotary  power  is 
greatly  dependent  on  temperature  and  concentra- 
tion. Calcium  forms  a  compound  with  Isevulose 
that  is  only  slightly  soluble.  The  corresponding 
glucose  compound  is  easily  soluble. 

EXPERIMENTS.  (1)  Prepare  osazone  crystals  from 
dextrose  and  Isevulose  as  follows:  To  10  c.c.  of  a 
strong  solution  of  the  sugar  add  0.25  gin.  of  phenyl- 


CARBOHYDRATES  AND  GLUCOSIDES  239 

hydrazine  hydrochloride  and  0.5  gm.  of  sodium 
acetate,  heat  in  a  boiling  water  bath  for  an  hour, 
and  cool.  Examine  the  yellow  crystals  under  the 
microscope.  Collect  the  crystals  on  a  filter,  wash 
thoroughly  with  cold  acetone  or  water  acidulated  with 
acetic  acid,  press  between  filter-paper,  recrystallize 
from  a  little  80%  alcohol,  dry  the  crystals  in  a  desic- 
cator, and  later  make  melting-point  determinations.1 
The  osazones  of  the  important  sugars  have  the 
following  melting-points : 

Dextrose  I 204°-205° 

Lactose 200° 

Maltose 206° 

(2)  Ketose  test.    To  5  c.c.  of  laevulose  solution 
add  5  c.c.  of  25%  HC1.     Add  a  little  resorcin  and 
heat  the  mixture.     A  deep  red  color  develops,  and 
later  a  brown  precipitate,  which  is  soluble  in  alcohol. 
The  alcoholic  solution  is  red. 

(3)  (a)  Try  the  aldehyde  tests  (see  p.  153)  with 
dextrose  solution.     (6)  To  some  dextrose  solution 
add  one-fifth  its  volume  of  alkaline  bismuth  reagent 
(4  gm.  Rochelle  salt  and  2  gm.  of  bismuth  sub- 
nitrate  dissolved  in  100  c.c.  of  10%  NaOH),  and 
boil  five  minutes.     On  cooling  a  black  precipitate 
separates  out. 

1 A  quicker  and  more  satisfactory  way  of  securing  osazone 
crystals  is  as  follows:  To  0.5  c.c.  phenylhydrazine  (base)  add 
0.5  c.c.  glacial  acetic  acid;  after  mixing  add  10  c.c.  of  the 
sugar  solution,  and  heat  in  a  boiling  water-bath;  glucosazone 
crystals  appear  in  5-10  minutes.  For  lact-  and  maltosazone, 
heat  20-30  minutes,  then  cool  before  examining. 


'240  ORGANIC  CHEMISTRY 

Several  heptoses  and  octoses  and  two  nonoses  are 
known,  but  they  are  unimportant. 

DISACCHARIDES 

These  are  the  result  theoretically  of  the  union  of 
two  monosaccharide  molecules,  with  the  elimination 
of  a  molecule  of  water,  cane  sugar  being  a  combina- 
tion of  dextrose  and  Isevulose,  lactose  of  dextrose 
and  galactose,  and  maltose  of  two  a-d-glucose 
molecules  : 


By  hydrolysis  the  constituent  monosaccharides  are 
easily  obtained: 


Dilute  mineral  acids  and  ferments  (invertases)  bring 
about  this  hydrolysis,  which  is  called  inversion. 
Yeast  produces  an  invertase  that  hydrolyzes  maltose 
quickly  and  another  that  hydrolyzes  cane  sugar 
slowly,  but  none  that  has  an  effect  on  lactose. 
Therefore  lactose  does  not  ferment  with  yeast, 
while  cane  sugar  and  maltose  do. 

Inversion  by  the  action  of  dilute  mineral  acids  is 
due  to  catalytic  action  of  hydrogen  ions,  just  as  in 
the  case  of  hydrolysis  of  esters  (p.  180)  (see  appen- 
dix, p.  452). 

Maltose  and  lactose  reduce  alkaline  copper  and 
bismuth  solutions;  pure  cane  sugar  does  not.  After 
inversion,  however,  cane  sugar  reduces  these 
reagents.  Therefore  Fehling's  solution  can  be  used 
for  quantitative  estimation  of  all  the  sugars  treated 


CARBOHYDRATES  AND  GLUCOSIDES  241 

of  in  this  chapter.     10  c.c.  of  Fehling's  solution  is 
reduced  by 

0.048    gram  dextrose. 
0.051        "     Isevulose. 
0.0676     "     lactose  (+H20). 
0.074       "     maltose. 

0.0475     "     cane  sugar  (after  conversion  into 
invert-sugar) . 

A  solution  of  copper  acetate  acidified  with  acetic 
acid  (Barfoed's  reagent)  is  not  reduced  quickly  to 
cuprous  oxide  by  disaccharides,  but  is  so  reduced 
by  monosaccharides. 

Maltose  and  lactose  form  osazones  with  phenyl- 
hydrazine,  each  of  these  having  a  characteristic 
crystalline  form  and  melting-point  (see  p.  239), 
while  cane  sugar  forms  no  such  combination  pro- 
vided hydrolysis  is  guarded  against. 

In  order  to  explain  the  non-aldehydic  action  of 
cane  sugar  as  shown  by  its  behavior  in  these  two  re- 
actions, the  following  formula  has  been  suggested 
for  it : 

CH2OH  CH2OH 

HO— C— H 


242 


ORGANIC  CHEMISTRY 


Both  the  aldehyde  and  ketone  groups  are  tied  up 
by  the  linking  together  of  their  C  atoms. 

The  other  disaccharides  have  the  following  for- 
mulae: 

Maltose. 
CH2OH  —          -CH2 

HO— C— H 
C— H 


H— C— OH 
HO— C— H 


H— C— OH 

a-d-glucose) 


HO— C— H 
C— H 


H— C— OH 


i-H 


(d-galactose 


HO— 


H— C— OH 

d-glucose) 


These  disaccharides  are  all  dextrorotatory.  Mal- 
tose shows  the  greatest  rotary  power,  lactose  the 
least;  maltose  and  lactose  manifest  multirotation. 
Lactose  solution  contains  a  and  &  lactose  in  equilib- 


CARBOHYDRATES  AND  GLUCOSIDES  243 

rium;  /3  lactose  has  the  formula  above  but  with  the 
end  group  arranged  as  in  jS-d-glucose.  Invert- 
sugar  is  distinctly  Isevorotatory,  while  the  cane  sugar 
from  which  it  is  produced  is  dextrorotatory;  this  is 
due  to  the  fact  that  the  Isevulose  produced  (invert- 
sugar  is  a  mixture  of  equal  parts  of  Isevulose  and  dex- 
trose) rotates  polarized  light  more  to  the  left  than 
does  dextrose  to  the  right. 

The  rotary  power  of  maltose  is  decreased  by  in- 
version, while  that  of  lactose  is  increased. 

Saccharose  (cane  sugar,  beet  sugar,  sucrose), 
Ci2H22On,  is  the  most  important  of  the  sugars 
because  of  its  use  as  food.  It  is  contained  in  sugar 
cane,  beets,  the  sap  of  certain  maple  trees,  and  in 
many  other  vegetables  and  plants. 

The  method  of  commercial  preparation  of  cane 
sugar  is,  in  brief,  as  follows:  The  juice  is  obtained 
from  the  sugar  cane  by  shredding  and  then  crush- 
ing the  cane  between  rollers.  The  sugar  beet,  how- 
ever, is  cut  into  slices  and  these  are  soaked  with 
successive  portions  of  hot  water,  the  sugar  diffusing 
out  of  the  beet  pulp.  The  sugar  extract  is  treated 
with  lime  (which  removes  acids  and  many  im- 
purities), then  with  carbon  dioxide  (which  removes 
the  excess  of  lime),  and  is  then  evaporated  in  vacuum 
pans.  On  cooling,  sugar  crystallizes  out.  This 
crude  sugar  is  dissolved,  filtered  through  bone- 
black  (animal  charcoal),  evaporated,  and  recrystal- 
lized.  The  syrup  that  is  left  is  molasses.  Cane 
sugar  as  sold  is  commonly  called  granulated  sugar. 

Cane  sugar  forms  large  crystals  when  slowly 
crystallized;  they  are  monoclinic  prisms.  It  melts 


244  ORGANIC  CHEMISTRY 

at  160°;  at  210°-220°  it  is  converted  into  caramel 
with  loss  of  water.  It  is  extremely  soluble,  100 
gm.  of  water  at  15°  dissolving  197  gm.  of  sugar; 
this  saturated  solution  has  a  specific  gravity  of 
1.329.  It  forms  saccharates  with  bases. 

Its  rotary  power  is  influenced  somewhat  by  con- 
centration; it  is  lessened  by  presence  of  acids, 
alkalies  or  salts,  but  it  is  practically  uninfluenced 
by  temperature. 

Lactose  (milk  sugar),  C^H^On+EbO,  is  the 
sugar  contained  in  milk.  It  occasionally  occurs  in 
the  urine  of  pregnant  and  nursing  women.  Cer- 
tain microorganisms  convert  lactose  into  lactic  acid. 
When  heated  it  forms  lactocaramel,  CeHioOs. 
Lactose  is  crystalline  and  contains  a  molecule 
of  water  of  crystallization.  It  can  be  obtained  as 
amorphous  lactose,  which  is  anhydrous.  Lactose 
forms  compounds  with  bases.  Its  specific  rotation 
is  not  influenced  much  by  concentration  or  temper- 
ature. 

Maltose,  C^B^On+EbO,  is  the  product  of  the 
action  of  the  ferments  diastase  (in  malt),  ptyalin 
(in  saliva),  or  amylopsin  (in  pancreatic  juice)  upon 
starch.  It  can  also  be  obtained  from  starch  by 
treatment  with  dilute  mineral  acids,  the  action  of 
the  acid  being  stopped  at  a  stage  before  glucose  is 
formed.  It  crystallizes  in  fine  needles.  Its  specific 
rotation  varies  with  concentration  and  tempera- 
ture. 

Isomaltose  (gallisin)  is  distinguished  from  maltose 
in  that  it  does  not  ferment  with  yeast,  and  that  its 
osazone  has  a  lower  melting-point  (150°). 


CARBOHYDRATES  AND  GLUCOSIDES  245 

EXPERIMENTS,  (1)  Produce  osazone  crystals 
from  lactose  and  from  maltose  (footnote,  p.  239). 
When  the  solutions  have  cooled,  examine  micro- 
scopically. Make  melting-point  determinations. 

(2)  (a)  Examine  a  10%  solution  (10  gm.  dissolved 
in  enough  water  to  make  100  c.c.  of  solution)  of  pure 
cane  sugar  with  the  polariscope  (see  p.  226).     (6)  To 
50  c.c.  of  a  20%  cane  sugar  solution  in  a  100  c.c.  grad- 
uated flask  add  1  gm.  of  citric  acid,  and  heat  in  a  boil- 
ing water-bath  for  30  minutes.     Cool,  almost  neu- 
tralize,  and  fill  up   to   the  mark.     Examine  this 
invert-sugar  solution  (corresponding  in  concentra- 
tion to  the  solution  in  (a)  with  the  polariscope.1 
The  specific  rotation  [a]D  of  the  important  sugars 
in  10%  solution  (at  20°)  when  sodium  light  is  used 
is  as  follows: 

Dextrose  (anhydrous) +52.5° 

Lsevulose -  93.0° 

Maltose  (anhydrous) +137.04° 

Lactose  (+H20) +52.5° 

Cane  sugar +  66 . 54° 

Invert  sugar -  20.2° 

Galactose +  81 .0° 

(  —  means  rotation  to  the  left.) 

(3)  Test  cane  sugar  before  and  after  inversion 
(solutions  of  experiment  2,  a  and  6)  with  Fehling's 
solution. 

(4)  Try  the  ketose  test   (see  p.   239)   on  cane 
sugar. 

M  100  X  rotation  observed 

>  For  calculation,  %  sugar  °[a]Oxdecimeters  tube  length- 


246  ORGANIC  CHEMISTRY 

(5)  Galadose  test.  To  10  c.c.  of  a  strong  solution  of 
lactose  add  3  c.c.  of  HNOs  and  boil  for  a  few  min- 
utes. Now  evaporate  on  a  water-bath  to  about 
3  c.c.  while  stirring.  Add  2  c.c.  of  water  and  cool. 
If  no  crystals  of  mucic  acid  separate  out,  let  the 
material  stand  and  examine  after  twenty-four  hours. 

The  trisaccharide  mffinose,  consists  of  d-fructose, 
d-glucose  and  d-galactose  linked  together  as  in 
saccharose,  none  of  the  CO  groups  being  free.  It 
therefore  does  not  reduce  nor  give  an  osazone. 
Emulsin  hydrolyzes  it  to  cane  sugar  and  galactose. 
Invertase  of  yeast  hydrolyzes  it,  therefore  it  fer- 
ments. It  gives  the  ketose  test.  Its  specific 
rotation  is  +104°, 

POLYS  ACCHARIDES 

These  have  complex  molecules,  the  empirical 
formula  of  each  being  an  unknown  multiple  of 


Cellulose,  (C6Hi005)^  or  (Cel^C^OH^X  of 
high  molecular  weight,  is  essential  to  all  plants, 
being  the  basis  of  the  woody  fiber.  Cotton-fiber, 
hemp,  flax,  and  the  best  filter-paper  are  almost 
entirely  cellulose.  Ordinary  paper  is  composed 
mainly  of  cellulose.  Cellulose  is  affected  by  only 
a  few  chemical  agents;  concentrated  acids  and  alka- 
lies and  an  ammoniacal  solution  of  copper  oxide 
(Schweitzer's  reagent)  are  able  to  dissolve  it.  If 
unsized  paper  be  treated  momentarily  with  sulphuric 
acid,  its  surfaces  become  changed  to  amyloid,  which 
renders  the  paper  tough  when  dried.  Parchment 
paper  is  made  in  this  way.  If  a  solution  of  cellulose 


CARBOHYDRATES  AND  GLUCOSIDES  247 

in  sulphuric  .acid  be  diluted  and  boiled,  dextrin  and 
glucose  are  produced  by  hydrolysis  of  the  cellulose. 

EXPERIMENTS.  (1)  Dissolve  some  scraps  of  filter- 
paper  in  a  little  cold  concentrated  B^SCU,  dilute 
with  200  c.c.  of  water,  and  boil  for  an  hour.  Neu- 
tralize some  of  this  hydrolyzed  cellulose  solution 
and  test  with  Fehling's  solution. 

(2)  Immerse  a  piece  of  blotting-paper  in  80% 
H2S04   for   a   moment   only,    transfer   to   a   large 
beaker  of  water,  and  wash  out  the  acid  thoroughly. 
Allow  the  paper  to  dry  out;   it  will  be  found  to  be 
tough. 

(3)  Detection   of   lignin 1   in   paper   made   from 
wood.     Coat  a  sheet  of  cheap  white  paper  with  a 
solution  of  aniline  in  HC1;  if  it  turns  yellow,  lignin 
is  present. 

Esters  of  cellulose  can  be  formed  by  the  action  of 
reagents  that  attack  alcoholic  hydroxyl  groups  (as 
acetic  anhydride). 

When  cellulose  is  treated  with  nitric  acid  in  the 
presence  of  sulphuric  acid,  nitro-celluloses  are  formed, 
just  as  nitroglycerol  is  produced  from  glycerol. 
These  range  from  mononitro-  to  trinitrocellulose. 

Guncotton  (nitrocellulose,  pyroxylin)  is  trinitro- 
cellulose. It  is  explosive.  By  dissolving  gun- 
cotton  in  acetone  a  gelatinous  mass  is  obtained; 
then  on  removing  the  solvent,  the  guncotton  is 
left  in  such  a  physical  condition  that  it  burns  and 
explodes  more  slowly.  This  substance  is  used  in 

1 A  substance  present  with  cellulose  in  wood;  it  is  supposed 
to  contain  pentosans  and  aromatic  bodies. 


248  ORGANIC  CHEMISTRY 

smokeless  powders.  The  products  of  the  explosion 
are  nitrogen,  hydrogen,  carbon  monoxide  and 
dioxide,  and  water-vapor. 

The  two  lower  nitrates  are  contained  in  celloidin. 
Collodion  is  a  solution  of  these  nitrates  in  a  mixture 
of  ether  and  alcohol.  Celluloid  is  made  by  dis- 
solving them  in  camphor  with  the  aid  of  a  little 
alcohol. 

An  artificial  silk  can  be  produced  by  means  of  trinitrocellulose, 
fine  filaments  being  made  and  spun  into  thread.  After  being 
woven  the  nitrocellulose  fabric  is  treated  with  a  solution  of 
calcium  sulphide,  which  removes  the  N02  groups.  Almost 
pure  cellulose,  resembling  silk,  is  left.  Artificial  silk  is  pro- 
duced by  two  other  methods,  one  of  these,  called  the  viscose 
method,  is  supplanting  the  others.  Viscose  silk  is  made  from 
as  pure  cellulose  as  can  be  obtained  from  wood  pulp.  The  latter 
is  treated  with  NaOH  solution  and  CS2,  and  is  macerated  for  a 
considerable  time.  The  cellulose  solution  is  squirted  through 
very  fine  openings  into  an  acid  bath  which  precipitates  the 
cellulose  as  fibers.  Large  quantities  of  artificial  silk  are  now 
produced. 

EXPERIMENT.  Mix  5  c.c.  of  C.P.  HNOs  and  10 
c.c.  of  C.P.  B^SO*.  When  it  is  cool,  immerse  some 
absorbent  cotton  in  the  mixture  for  half  a  minute, 
then  wash  out  the  acid  from  the  cotton  with  a  large 
quantity  of  water,  press  out  the  water,  and  dry  at 
room  temperature.  When  dry,  shake  part  of  it 
with  a  mixture  of  ether  and  alcohol,  pour  the  liquid 
into  an  evaporating  dish  and  allow  to  evaporate.  A 
syrupy  liquid  (collodion)  is  obtained,  and  later  a 
glassy  skin.  Test  the  inflammability  of  another 
piece  of  the  dry  cotton,  and  compare  with  un- 
treated cotton. 


CARBOHYDRATES  AND  GLUCOSIDES  249 

Starch  (amylum),  (CeHioOs)^,  comprises  a  large 
part  of  all  vegetable  food.  It  exists  in  the  plant  as 
granules,  having  different  forms  and  sizes  in  dif- 
ferent plants.  Starch  grains  are  spherocrystals, 
covered  with  a  layer  of  specially  modified  starch 
substance  which  is  more  resistant  to  the  action  of 
water,  ferments  and  chemical  agents  than  the  sub- 
stance within  the  grains. 

Starch  and  cellulose  are  probably  synthesized  by 
plants  from  formaldehyde  by  processes  of  conden- 
sation and  polymerization. 

Ordinary  starch  is  made  from  corn  or  potatoes. 
Starch  is  insoluble  in  cold  water.  When  boiled,  it 
apparently  goes  into  solution  or  forms  a  gelatinous 
mass,  according  to  the  amount  of  water  present. 
It  is  a  colloidal  solution  containing  also  tiny  masses 
in  suspension. 

It  is  precipitated  from  solution  by  low  concen- 
tration of  alcohol,  and  by  saturation  with  certain 
salts  (as  Na2S(>4  and  NaCl).  A  dilute  solution  of 
boiled  starch  is  readily  hydrolyzed  by  ferments 
(diastase,  ptyalin,  etc.)  and  by  platinum  black 
(catalytic  action)  at  a  temperature  of  about  40°. 
Dextrin  is  first  formed,  then  maltose,  while  hydrolysis 
by  boiling  with  dilute  mineral  acid  carries  the  proc- 
ess further,  the  end  product  being  glucose.  Heat 
alone  converts  starch  into  dextrin;  the  crust  on 
bread  is  mainly  dextrin.  Starch  takes  up  iodine, 
probably  by  adsorption,  thus  forming  a  blue  sub- 
stance; heat  drives  the  iodine  from  this  substance, 
so  that  the  color  is  lost  until  the  mixture  becomes 
cool  again.  Natural  starch  contains  two  dif- 


250  ORGANIC  CHEMISTRY 

ferent  materials,  a  soluble  substance  amylose 
(60-80%  of  the  weight  of  the  starch)  and  an  insolu- 
ble substance,  amylopectin,  which  gelatinizes  with 
hot  water.  Amylopectin  gives  little  color  with 
iodine,  while  amylose  gives  a  deep  blue.  Both  are 
hydrolyzed  by  ferments.  It  is  probable  that  there 
is  a  very  large  number  of  amyloses  (stereoisomers). 

Dextrins  are  less  complex  bodies  than  starch. 
The  intermediate  substances  between  starch  and 
maltose  formed  during  digestion  are,  in  the  order 
of  complexity,  amylodextrins,  erythrodextrins, 
achroodextrins,  and  maltodextrins.  The  first  gives 
a  blue  color  with  iodine,  the  second  a  red  or  reddish 
brown  (a  mixture  of  erythro-  and  amylo-dextrins 
gives  a  bluish  red  color),  while  the  simpler  dextrins 
give  no  color  test.  Commercial  dextrin  is  prepared 
from  starch  by  means  of  heat.  It  forms  a  gummy 
solution,  which  is  used  for  making  labels.  It  is 
insoluble  in  alcohol.  Most  dextrins  are  precipitated 
by  saturating  their  solutions  with  salts,  such  as 
ammonium  sulphate  and  sodium  sulphate.  Most 
dextrins  are  precipitated  by  alcohol  when  the 
concentration  reaches  75%;  the  lower  dextrins 
require  as  much  as  90%  for  precipitation. 

The  dextrins  are  dextrorotatory,  the  (a)D  being 
192-196°  for  the  higher  dextrins.  Acid  hydrolyzes 
them  to  glucose.  Diastatic  ferments  change  them 
to  maltose. 

Glycogen,  (CeHioOs)^,  resembles  dextrin.  It  is 
present  in  animal  tissues,  mainly  in  the  liver.  The 
liver  acts  as  a  storehouse  for  carbohydrates,  storing 
up  in  the  form  of  glycogen  the  sugar  that  comes  to 


CARBOHYDRATES  AND  GLUCOSIDES  251 

it  from  the  digestive  organs,  and  then  reconverting 
the  latter  into  sugar  as  needed  by  the  tissues.  A 
substance  has  been  found  in  certain  vegetables 
resembling  glycogen.  Glycogen  forms  a  colloidal 
solution,  which  is  characteristically  opalescent. 
With  iodine  it  gives  a  reddish  brown  color.  Its 
(a)D  is  +196.5°.  It  hydrolyzes  to  dextrose.  Di- 
astatic  ferments  form  from  it  dextrins,  and  finally 
maltose.  It  is  precipitated  by  55%  alcohol  and 
by  basic  lead  acetate. 

EXPERIMENTS.  (1)  Test  solutions  of  starch,  dex- 
trin, and  glycogen  with  iodine  solution. 

(2)  Test  them  with  lead  subacetate  solution. 

(3)  Test    them   with    Fehling's    solution    before 
and  after  hydrolyzing  by  boiling  with  dilute  HC1. 

Gums  contain  polysaccharides  similar  to  dextrin. 
Gum  arabic  (acacia)  contains  a  pentosan,  araban, 
(CsHsO^n  which  hydrolyzes  to  Z-arabinose.  Gum 
tragacanth  contains  bassorin. 

Agar-agar  is  a  pectin-like  substance  containing 
at  least  seven  different  carbohydrates,  including 
some  starch  and  cellulose.  The  most  important 
constituent  is  gelose,  a  galactan,  which  can  be 
hydrolyzed  to  galactose. 

GLUCOSIDES 

Natural  glucosides  are  vegetable  substances  which 
can  be  split  up  by  hydrolysis  into  a  sugar  (or  sugars) 
and  some  other  characteristic  organic  compound  or 
compounds.  Many  of  them  are  important  medi- 


252  ORGANIC  CHEMISTRY 

cines.  A  large  number  of  glucosides  have  been 
studied.  The  sugar  derived  from  them  is  generally 
glucose. 

Phloridzin,  C2iH24Oio,  is  used  to  produce  exper- 
imental diabetes  in  animals.  It  splits  up  into 
glucose  and  phloretin,  Ci5Hi405  (see  also  phloro- 
glucin,  p.  348). 

Arbutin,  Ci2Hi607,  is  a  comparatively  simple 
glucoside,  hydrolyzing  to  dextrose  and  hydro- 
quinone. 

Gaultherin,  CuHigOs,  is  a  glucoside  contained 
in  the  wintergreen  plant;  an  accompanying  ferment 
hydrolyzes  it  to  dextrose  and  methyl  salicylate. 

Salicin,  CisHigOy,  is  used  in  medicine;  it  hydro- 
lyzes to  dextrose  and  saligenin  (p.  354).  Its  struc- 

/O-CeHnOs 

tural  formula  is  C6H4<  ^TT  ^TT 

M^£i2Uil 

Amygdalin,  C2oH27NOii,  is  found  in  bitter  almonds, 
peach-pits,  etc.  The  ferment  emulsin,  as  well  as 
acids,  hydrolyzes  it  to  glucose,  hydrocyanic  acid, 
and  benzaldehyde  (see  p.  351). 

Its  structural  formula  is  said  to  be: 


O 

CH(CHOH)  2CH  •  CHOH  -  CH2 


>CH  (CHOH)2CH-CHOH-CH2OH. 

I. 

C6H5— CH— CN 


CARBOHYDRATES  AND  GLUCOSIDES  253 

Digitalin,  CasHseOi*,  an  active  principle  of  digi- 
talis, hydrolyzes  to  dextrose,  digitaligenin,  C22H3o03, 
and  digitalose,  CrHuOs. 

Digitoxin,  C34H540ii,  the  chief  active  glucoside 
of  digitalis,  yields  by  hydrolysis  digitoxigenin, 
C22H32C>4,  and  digitoxose,  Cell  1204. 

Strophanthin,  C4oH660i9,  from  strophanthus, 
hydrolyzes  to  strophanthidin,  C2?H38O7,  methyl 
alcohol,  mannose  and  rhamnose. 

Sinigrin,  CioHi8NS2KOio,  the  glucoside  of  black 
mustard,  by  the  action  of  a  ferment  present  in 
the  mustard  splits  up  into  mustard  oil,  dex- 
trose, and  KHS04.  In  similar  manner  sinalbin, 
C3oH44N2S2Oi6,  of  white  mustard  yields  dextrose, 
parahydroxytolyl  mustard  oil  and,  sinapin  bisul- 
phate. 

Indican,  CuHiyOeN,  is  the  glucoside  which  is 
contained  in  those  plants  from  which  indigo  is 
produced.  It  is  a  combination  of  glucose  and 
indoxyl.  The  indican  present  in  urine  (p-  417) 
is  a  different  compound. 

Saponins.  A  large  number  of  glucosides  are 
grouped  together  into  this  sub-class.  They  are 
non-nitrogenous  and  form  solutions  that  foam  on 
shaking  (cf.  soaps). 

Digitonin  is  a  saponin  contained  in  digitalis, 
C54H92O28;  it  splits  up  into  digitogenin,  CsoH^sOe, 
and  two  molecules  each  of  glucose  and  galactose. 

Artificial  glucosides  are  simpler  compounds;  for 
example,  a  methyl  glucoside  of  d-glucose  has  the  CHs 
group  attached  to  O  of  the  aldehyde  group  of 
glucose. 


254  ORGANIC  CHEMISTRY 

EXPERIMENTS.  (1)  Try  Molisch's  test  (see  p. 
234)  on  a  solution  of  a  glucoside. 

(2)  Hydrolyze  some  glucoside  solution  by  boil- 
ing with  dilute  H2S04,  neutralize,  and  examine  for 
sugar  with  Fehling's  solution. 


CHAPTER  XVIII 

NITROGEN  DERIVATIVES.    (ALSO  PHOSPHORUS  AND 
ARSENIC  COMPOUNDS) 

NITROGEN  DERIVATIVES 

THESE  fall  into  four  classes:  (1)  cyanogen 
derivatives,  (2)  substituted  ammonias,  (3)  nitro 
compounds,  and  (4)  nitrites. 

Cyanogen  Derivatives.  Organic  cyanides  can  be 
prepared  by  treatment  of  alkyl  halides  with  potas- 
sium cyanide,  as 

C2H5|cf +K|CN  =  C2H5CN +KC1, 

(Ethyl  chloride) (Ethyl  cyanide) 

also  by  anhydrolysis  (removal  of  water)  of  an  acid 
amide  (see  p.  273),  thus  (see  exp.): 

CH3  •  CONH2  =  CH3  •  CN  +H2O. 

(Acetamide)  (Methyl  cyanide) 

EXPERIMENT.  Into  a  dry  250-c.c.  wide-mouth 
Jena  flask  (extraction  flask)  put  10  gm.  of  dry 
acetamide  and  add  quickly  about  15  gm.  of  phos- 
phorus pent  oxide.  Mix  quickly  with  a  dry  rod. 
As  soon  as  possible  add  10  gm.  more  of  the  oxide 
as  a  top  layer.  Cork  and  connect  with  a  condenser 
immediately.  Heat  with  a  small  smoky  flame. 

255 


256  ORGANIC  CHEMISTRY 

Collect  the  distillate  in  a  large  clean  test-tube. 
Shake  the  distillate  with  half  its  volume  of  water, 
then  add  small  pieces  of  solid  KOH  until  no  more 
dissolves,  keeping  the  solution  cool  with  running 
water;  the  cyanide  now  separates  as  a  top  layer. 
Transfer  to  a  narrow  test-tube,  and  remove  the 
cyanide  carefully  with  a  clean  dry  pipette.  Use 
the  product  for  synthesis  of  acetic  acid  (p.  171). 

The  CN  group  of  organic  cyanides  can  be 
hydrolyzed  to  COOH;  in  consequence  the  alkyl 
cyanides  are  called  acid  nitriles;  for  example, 
CHs-CN  is  acetonitrile  because  acetic  acid  can  be 
obtained  from  it  (see  exp.,  p.  171) : 

CH3CN  +2H2O  =  CH3  •  COOH  +NH3(i.e., 

CH3COONH4.) 

HCN,  hydrocyanic  acid,  may  be  called  formonitrile  because 
it  can  be  hydrolyzed  to  formic  acid.  As  regards  acid  power  it 
is  extremely  weak;  its  dissociation  constant  is  less  than  one 
ten-thousandth  of  that  of  acetic  acid.  It  is  very  poisonous, 
but  is  used  in  2%  solution  as  a  remedy. 

This  reaction  also  shows  that  the  carbon  atom  of 
CN  is  linked  directly  to  the  carbon  chain.  There 
are  cyanides,  however,  in  which  it  is  the  nitrogen 
atom  of  the  CN  group  that  is  linked  to  the  carbon 
chain.  These  are  isocyanides  or  isonitriles. 
CH3— NEEEC  is  methyl  ixocyanide. 

Some  chemists  think  that  hydrocyanic  acid  may 
be  a  mixture  of  HCN  and  HNC,  and  that  the 
metallic  cyanides  are  mainly  isocyanides. 

Chloroform  when  heated  with  alkali  and  a  primary 


NITROGEN  DERIVATIVES  257 

amine  gives  rise  to  the  disagreeable  vapor  of  iso- 
cyanide  : 

CHC13  +R—  NH2  =R—  NC  +3HC1. 


When  an  isocyanide  is  hydrolyzed,  an  amide  and 
formic  acid  are  formed: 

CH3  •  NC  +2H2O  -  CH3NH2  +HCOOH. 

EXPERIMENT.  Isocyanide  reaction.  Mix  to- 
gether in  a  test-tube  a  few  drops  of  chloroform, 
1  c.c.  of  aniline,  and  2  c.c.  of  alcoholic  KOH.  Warm 
gently.  Note  the  peculiar  disagreeable  odor  of 
the  isocyanide.  As  soon  as  this  odor  is  detected, 
dilute  the  mixture  with  much  water  in  the  sink, 
since  the  fumes  are  poisonous. 

Other  Cyan-compounds. 

Cyanic  acid  may  be  HO—  C=N  or  HN=C=0,  or 
a  mixture  of  both. 

Sulphocyanic  (thiocyanic)  acid  has  sulphur  re- 
placing O  in  the  cyanic  acid  molecule. 

Cyan-acids,  e.g.,  cyan-acetic  acid,  CH2CN-COOH, 
are  analogous  to  monochloracetic  acid.  Such  an 
acid  is  much  stronger  than  the  simple  acid  and 
even  stronger  than  the  corresponding  monochlor 
acid. 

Substituted  Ammonias.  These  may  be  considered 
as  ammonia  in  which  one  or  more  hydrogen  atoms 
are  replaced  by  organic  groups.  Primary  substituted 

/H 

ammonias,  N^-H,  contain  the  group   NH2,  called 
XR 


258  ORGANIC  CHEMISTRY 

the  amido  or  amino  group.    Secondary  substituted 

/H 
ammonias,  N£-R,  contain  the  imido   group,   NH. 

XR 

/R 
Tertiary  substituted  ammonias,  N^-R,  have  all  the 

XR 

hydrogen  of  ammonia  displaced. 

These  are  all  called  amines.  They  are  pre- 
pared by  the  action  of  ammonia  on  alkyl  halides: 

C2H5Br +NH3  =  C2H5NH2  •  HBr, 

(Ethylamine  hydrobromide) 

C2H5NH2  +C2H5Br  =  (C2H5)2NH  •  HBr, 

(Diethylamine  hydrobromide) 

(C2H5)2NH  +C2H5Br  =  (C2H5)3N  •  HBr. 

(Triethylamine  hydrobromide) 

The  HBr  is  removed  by  treating  the  above  com- 
pounds with  KOH. 

Amines  form  salts  with  acids  by  adding  on  the 
entire  acid  molecule,  N  changing  its  valence  from 
three  to  five.  The  salts  of  alkaloids  are  of  similar 
nature. 

Some  amines  have  two  NH2  groups,  as  ethylene 
diamine,  NH2— CH2  -  CH2— NH2. 

The  amines  may  also  be  prepared  by  treating  an 
acid  amide  with  sodium  hypobromite  (see  exp.): 

CH3  •  CONH2  +Br2  +4NaOH  =  CH3  •  NH2  +2NaBr 

(Acetamide)  (Methylamine) 

+Na2CO3-t-2H2O. 
(Br  forms  hypobromite  with  NaOH.) 


NITROGEN  DERIVATIVES  259 

EXPERIMENT.  Treat  12.5  gm.  of  dry  acetamide 
in  a  half -liter  flask  with  11.5  c.c.  of  bromine;  add 
a  cooled  solution  of  20  gm.  of  KOH  in  175  c.c.  of 
water  until  the  mixture  turns  a  bright  yellow,  mean- 
while keeping  the  flask  cooled  with  running  water. 
Run  this  hypobromite  mixture  by  means  of  a  drop- 
ping funnel  rapidly  into  a  solution  of  40  gm.  of 
KOH  in  75  c.c.  of  water.  Keep  the  temperature  of 
the  liquid  at  70-75°.  Cool  the  flask  if  the  temper- 
ature gets  above  75°.  Keep  at  75°  for  thirty  min- 
utes. Add  some  powdered  pumice  and  distill  on 
a  sand-bath.  Attach  an  adapter  (see  Fig.  19, 
p.  126)  to  the  condenser;  dip  this  slightly  below  the 
surface  of  strong  hydrochloric  acid  in  the  receiving 
flask  (50  c.c.  C.P.  HC1+50  c.c.  of  water).  Distill 
until  the  distillate,  tested  by  detaching  the  adapter 
momentarily,  is  no  longer  strongly  alkaline  to 
litmus.  Evaporate  the  acidulated  distillate  in  an 
evaporating  dish  heated  over  wire  gauze.  When 
down  to  small  bulk  complete  the  drying  in  an  oven 
at  110°.  Pulverize  the  residue;  treat  with  several 
portions  of  10  c.c.  of  hot  alcohol,  filtering  the  de- 
canted alcohol  into  a  dry  beaker.  Crystals  of 
methylamine  hydrochloride  separate  out  by  cool- 
info.  Filter  off  the  crystals;  press  between  filter- 
paper;  keep  part  as  a  specimen.  Put  the  rest  into 
a  small  test-tube,  and  add  strong  KOH  solution; 
methylamine  is  evolved.  Note  the  odor  and  the 
reaction  of  the  gas  to  litmus.  Test  its  inflam- 
mability by  corking  the  test-tube  with  a  cork 
fitted  with  a  glass  tube  that  has  a  finely  drawn 
tip,  and  applying  a  flame  to  this  tip.  Heat  the 


260  ORGANIC  CHEMISTRY 

mixture  if  necessary  to  secure  free  evolution  of 
gas. 

Nascent  hydrogen  converts  an  alkyl  cyanide  into 
an  amine, 

CH3CN  +4H  =  CH3  •  CH2NH2. 

(Methyl  cyanide)  (Ethylamine) 

Many  amines,  particularly  the  primary  ammonia 
bases,  are  decomposed  by  nitrous  acid.  This  is  a 
reaction  of  considerable  importance.  An  ammo- 
nium nitrite  derivative  is  formed  first,  but  this  is 
so  unstable  that  it  breaks  down,  liberating  nitrogen : 

NH2  •  C2H5  +HN02  =  NH3  (C2H6)  •  N02, 

(Ethylamine)  (Ethyl  ammonium  nitrite) 

NH3(C2H5)  •  NO2  =N2  +H20  +C2H5OH. 

Many  amines  result  from  decomposition  of 
protein  material.  Amines  resemble  ammonia  in 
odor,  and  their  vapors  are  alkaline  to  litmus.  When 
dissolved  in  water  they  form  bases,  i.e.,  they  give 
rise  to  hydroxyl  ions.  Many  of  the  amines  are 
more  strongly  basic  than  ammonium  hydroxide. 

There  are  quaternary  bases  in  which  four  organic 
groups  are  linked  to  nitrogen;  these  are  really  sub- 
stituted ammonium  compounds.  Tetraethyl  ammo- 
nium hydroxide  is  (C2H5)4NOH  (cf.  NH4OH). 
This  is  a  very  strong  base;  its  saponifying  power  is 
almost  equal  to  that  of  sodium  hydroxide.  If  the 
saponifying  power  (affinity  constant)  of  LiOH  be 
taken  as  100, 


NITROGEN  DERIVATIVES  261 

KOHandNaOH=98 

(C2H5)4NOH=79 

NH4OH=  2 

Methylamine,  dimethylamine,  and  trimethyla- 
mine  are  gases.  They  are  contained  in  herring- 
brine.  They  are  also  obtained  by  destructive  dis- 
tillation of  the  residue  that  is  left  after  preparing 
alcohol  from  the  molasses  of  beet  sugar.  HC1  is 
used  to  hold  the  amines  as  salts.  This  amine  dis- 
tillate is  used  commercially  to  produce  methyl 
chloride,  because  the  latter  can  be  obtained  from 
trimethylamine  by  treatment  with  hydrochloric 
acid: 

(CH3)3N—  HC1+3HC1  =3CH3C1+NH4C1. 

Choline  is  a  substituted  ammonium  hydroxide, 
trimethylhydroxyethyl  ammonium  hydroxide  : 


It  will  be  noticed  that  it  is  also  related  to  primary 
alcohols.     It  is  of  physiological  importance. 

Choline  is  oxidized  to  betaine  by  removal  of  the  H 
atoms  of  both  the  alcohol  and  the  basic  hydroxyl 
groups, 


(CH3) 


/ 

N\ 


CH2-CO 


262  ORGANIC  CHEMISTRY 

Analogous    to  choline  and    betaine  is  carnitine 
(novaine), 

/CH2.CH2-CH(OH).CO 

(CN3)3N< 

\0 


The  lecithins  are  salts  of  choline.  The  chief  one 
(distearyl  lecithin)  contains  stearic  and  glycerophos- 
phoric  acids  in  combination  with  choline,  having 
the  formula: 

CH2 OOCisH35   (Stearic  acid) 

CH— OOCi8H35 

/OH 


)H2— O— PCX — O— C2H4N(CH3)3OH 

(Glycerol)  (Phosphoric  acid)  (Choline) 

Lecithin  is  an  important  constituent  of  yolk  of  egg, 
of  nerve-tissue,  of  bile,  and  of  the  envelope  of  red 
blood-corpuscles. 

Phosphatides.  The  lecithins  belong  to  this  class 
of  compounds.  Phosphatides  contain  phosphoric 
acid  in  ester  combination  with  an  alcohol,  generally 
glycerol,  and  one  or  more  fatty  acid  radicles,  and 
also  one  or  more  radicles  containing  nitrogen, 
generally  choline.  They  are  of  importance  in 
biochemistry.  One  of  these  is  cephalin,  which  has 
been  obtained  from  brain  tissue.  It*  contains  the 
radicle  of  stearic  acid  and  of  an  unsaturated  acid 
of  the  linoleic  acid  series,  Ci7H3oCOOH,  while  the 
nitrogenous  part  differs  from  choline  in  having 
one  methyl  group  instead  of  three. 

Muscarine  is  closely  related  to   choline.     It  has 


NITROGEN  DERIVATIVES  263 

been  suggested  that  it  is  the  aldehyde  corresponding 
to  choline  considered  as  an  alcohol: 

CH2—  CHO(+H2O) 


Some  chemists  believe  that  the  CHO  group  is 
combined  with  water,  so  that  it  is  really  —  CH(OH)2 
as  in  chloral  hydrate. 

Muscarine  is  a  basic  substance  classed  as  an  alka- 
loid (see  p.  425).  It  is  very  poisonous  and  is  con- 
tained in  toadstools  (Agaricus  muscarius)  and  some 
other  plants. 

Many  ptomaines  1  are  amine  bases.  Methyla- 
mine,  dimethylamine,  trimethylamine,  ethylamine, 
diethylamine,  triethylamine,  propylamine,  butyl- 
amine,  amylamine,  muscarine,  and  xjholine  occur 
as  ptomaines. 

Cadaverine  and  putrescine  are  diamine  ptomaines. 

Cadaverine  is 

/CH2—  CH2-NH2 
H2\CH2—  CH2-NH2' 

Putrescine  has  the  formula, 

CH2—  CH2—  NH2 
CH2—  CH2—  NH2 

1  Ptomaines  are  organic  bases  formed  by  the  action  of  bac- 
teria on  nitrogenous  matter.  Decomposing  animal  tissue 
is  very  apt  to  contain  ptomaines.  Many  of  them  are  highly 
toxic  and  are  the  cause  of  death  in  certain  cases  of  poisoning 
by  canned  meats,  etc. 


264  ORGANIC  CHEMISTRY 

Neurine,  like  choline,   is  a  ptomaine-containing 
oxygen, 

H=CH2 


Urotropine  is  hexamethylentetramine, 
and  is  obtained  by  the  action  of  ammonia  on  for- 
maldehyde. 

Acid  solutions,  even  those  of  very  low  H  ion 
concentration,  act  on  urotropine,  liberating  for- 
maldehyde. 

Piperazine  (spermine)  is  diethylendiamine, 


Piperazine  acts  as  a  solvent  for  uric  acid,  pro- 
vided the  former  is  present  in  sufficient  concentra- 
tion. Sidonal,  lycetol,  and  lysidin  are  piperazine 
derivatives  and  are  used  for  the  same  purpose. 

Analogous  to  the  substituted  ammonias  are  the  substitu- 
tion derivatives  of  phosphine  (PH8)  and  arsine  (AsH3)  Since 
they  will  be  mentioned  in  no  other  place,  it  may  be  well  in 
this  connection  to  state  that  there  are  organic  acids  contain- 
ing phosphorus  or  arsenic,  as,  for  example,  cacodylic  acid, 
which  is  dimethylarsenic  acid, 

CH3 
CH3. 
OH 

Nitro  Compounds. — Nitroparaffins  have  N  of  the 
nitro  group  linked  directly  to  C  of  the  chain,  e.g., 
nitroethane,  CH3-CH2 — NO2.  The  nitro  com- 
pounds of  the  benzenes  are  much  more  important 


NITROGEN  DERIVATIVES  265 

than  are  those  of  the  paraffins,  and  will  be  considered 
later. 

The  Nitrites.  Ethyl  Nitrite,  C2H5— 0— NO,  and 
amyl  nitrite,  CsHn — 0 — NO,  are  of  importance. 
Both  are  used  as  medicines.  Amyl  nitrite  is  a  very 
valuable  remedy;  its  physiological  action  is  similar 
to  that  of  nitroglycerol  (see  p.  202),  but  comes  on 
quickly  and  is  very  evanescent.  It  consists  chiefly 
of  isoamyl  nitrite.  These  organic  nitrites  are  often 
called  nitrous  esters,  being  formed  by  the  action  of 
nitrous  acid  on  alcohols. 

EXPERIMENT.  Prepare  amyl  nitrite  as  follows: 
Mix  in  a  small  flask  20  c.c.  of  fermentation  amyl 
alcohol  and  15  gm.  of  finely  powdered  sodium  nitrite. 
Set  the  flask  in  ice- water;  add  to  the  alcohol, 
drop  by  drop,  5  c.c.  of  C.P.  H2SO4  from  a  dropping 
funnel.  Amyl  nitrite  forms  a  top  layer;  decant  it 
off  into  a  separating  funnel.  Add  some  water  to  the 
mixture  in  the  flask  and  shake;  when  more  amyl 
nitrite  separates  out,  decant  again.  Separate  the 
nitrite  from  the  aqueous  liquid.  Dry  with  calcium 
chloride  and  distill.  Note  the  color,  odor,  and  the 
effect  of  cautious  inhalation  (flushing  of  the  face 
and  vascular  throbbing), 


CHAPTER  XIX 

AMINO  ACIDS  AND  ACID  AMIDES 
AMINO  ACIDS 

Amino  or  amido  acids  are  acids  containing  an 
NH2  or  amido  group.  Corresponding  to  mono- 
chloracetic  acid,  CH2C1-COOH,  is  aminoacetic 
acid,  CH2NH2-COOH. 

The  simplest  amino  acid  is  aminoformic  acid, 
NH2-COOH,  called  carbamic  acid.  The  free  acid 
is  unknown.  The  salts  are  unstable,  showing  a 
decided  tendency  to  become  converted  into  car- 
bonates. Ammonium  carbamate  is  of  considerable 
importance  in  physiology,  because  it  is  believed  to 
be  one  of  the  forerunners  of  urea.  It  can  be  changed 
into  urea  by  heating  it  in  a  sealed  tube  at  a  temper- 
ature of  135-140°: 

NH2  -  COONH4  =  NH2  •  CO  -  NH2  +H2O. 

(Ammonium  carbamate)  (Urea) 

EXPERIMENT.  Prepare  ammonium  carbamate  by 
bubbling  dry  C02X  and  dry  NHs  simultaneously  into 
alcohol  contained  in  a  cylinder  or  graduate.  Secure 
the  dry  NHs  as  previously  described  (see  p.  153). 
Dry  the  CO2  by  bubbling  it  through  H2S04.  When 

1 C02  is  obtained  by  putting  marble  chips  into  a  bottle 
or  generator  and  adding  HC1  by  a  dropping  funnel. 

266 


AMINO  ACIDS  AND  ACID  AMIDES  267 

a  considerable  quantity  of  crystals  has  been  pro- 
duced, stop  the  process.  Filter  off  the  alcohol; 
press  the  crystals  between  filter-paper.  To  test 
the  carbamate,  dissolve  some  of  the  crystals  in  5  c.c. 
of  distilled  water  that  has  been  cooled  to  0°;  and 
immediately  add  some  cold  CaCl2  solution.  No 
reaction  is  apparent  because  calcium  carbamate 
in  solution  is  stable  at  very  low  temperatures. 
Now  warm  the  solution;  the  carbamate  decom- 
poses and  a  heavy  precipitate  of  calcium  carbonate 
appears.  Leave  the  rest  of  the  crystals  exposed 
to  the  air  several  days;  a  small  amount  of  a  white 
powder  (NH4HC03)  is  obtained: 


Ethyl  carbamate,  or  urethane,  NH2-COOC2H5,  is 
an  ester  having  a  hypnotic  action. 

Amino  acids  may  be  obtained  by  treating  a  halo- 
gen fatty  acid  with  ammonia,  thus: 


H2N|H +C1!H2C  •  COOH  =  NH2  -  CH2  •  COOH  +HC1. 

(Monochloracetic  acid)  (Aminoacetic  acid) 

Ammonium  salts  are,  of  course,  formed.  They 
can  also  be  obtained  by  decomposing  proteins  by 
means  of  acids,  alkalies,  or  hydrolytic  ferments. 

All  the  amino-acids  that  are  considered  in  this 
chapter  are  of  great  importance  in  physiology. 
They  are  very  weak  acids.  In  fact  they  are  am- 
photeric  electrolytes,  their  solutions  behaving  as 
if  they  contained  both  hydrogen  and  hydroxyl  ions. 


268  ORGANIC  CHEMISTRY 

The  arnino  group  gives  the  basic  character  to  the 
molecule.  Proteins  and  some  other  organic  com- 
pounds act  in  the  same  manner. 

Glycocoll  (glycin)  is  aminoacetic  acid, 

/NH2 
CH2^-— COOH. 

It  can  be  produced  from  glue  (or  gelatin)  by  boil- 
ing with  dilute  sulphuric  acid  or  baryta  water.  It 
can  be  prepared  by  allowing  an  excess- ^of  strong 
ammonium  hydroxide  to  act  on  monochloracetic 
acid  for  twenty-four  hours.  In  the  animal  body 
it  combines  with  benzoic  acid  to  form  hippuric 
acid  (see  p.  360),  and  with  cholic  acid  to  form  one  of 
the  bile  acids,  glycocholic  acid.  %  •'* 

/NH-CH3 

Methyl  glycocoll,  CH2<     ?  ,   is^alled   sar- 

\COOH 

cosin.  It  can  be  synthesized  from  monobromacetic 
acid  and  methylamine: 

CH2Br  -  COOH  +2CH3  •  NH2  =  CH</ 

MJOOH 


It  is  a  product  of  decomposition  of  creatin  and  of 
caffeine. 

Alanin,  CH3-CH'NH2-COOH,  is  a-aminopro- 
pionic  acid.  It  can  be  made  from  a-chlorpropionic 
acid  by  treatment  with  ammonia.  It  is  isomeric 
with  sarcosin. 

Serin  is  hydroxyalanin,  -  CH2OH  •  CHNH2  -  COOH. 


AMINO  ACIDS  AND  ACID  AMIDES  269 

Valin  is  a-aminoisovaleric  acid, 

/-ITT 

CH-CHNH2-COOH. 


Leucin  is  a-aminoisobutylacetic  acid,  or  a-amino- 
isocaproic  acid, 

/NH2 
>CH— CHa-r-CH— COOH. 

(Isobutyl)  (Aminoacetic  acid) 

This  may  occur  in  the  urine  in  certain  diseases.  It  is 
a  decomposition  product  of  protein,  being  an  im- 
portant end  product  of  tryptic  digestion. 

C2H5\  /NH2 

Isoleucin,  /CH — CH<f  ,  is  contained 

\  i  it  Q/  N(jOOrT 


, 
JOOH 

in  certain  proteins. 

Aspartic  acid  (asparaginic  acid)  is  aminosuccinic 
acid, 

/NH2 

COOH 


CH2  --  COOH 

It  is  obtainable  from  asparagin  and  from  protein. 

Glutaminic  acid  (glutamic  acid)  is  a-aminoglutaric 
acid, 

/NH2 

/CH^—  COOH 
r^TT  c 

2\CH2-COOH  ' 

Gelatin  and  caseinogen  can  be  split  up  so  as  to 
furnish  a  considerable  proportion  of  this  acid. 

Phenylalanin  and  tyrosin  are  aromatic  mono-amino- 
acids  derived  from  proteins  (see  p.  371).    The  ammo 


270  ORGANIC  CHEMISTRY 

acids  considered  thus  far  have  the  amino  group  in 
the  a-position. 
Lysin  is  ae-diaminocaproic  acid, 

/NH2 
NH2  •  CH2  •  CH2  •  CH2  -  CH2  -  CH<^  . 

It  is  one  of  the  products  of  protein  when  boiled  with 
mineral  acid. 

Ornithin  is  «s-diamino  valeric  acid, 

/NH2 

NH2  •  CH2  •  CH2  -  CH2  •  CH<;  ^  „  _. 

MJOOH 

Arginin  is  related  to  ornithin,  being   d-guanidin- 
a-aminovaleric  acid, 

_     /NH2 

:\NH^CH2.CH2-CH2.CH/NH2    . 

(Guanidin)  \COOH 

(a-Aminovaleric  acid) 

It  can.be  hydrolyzed  to  urea  and  ornithin,  thus  : 
_     /NH2 
\ 


NH—  CH2  •  CH2  •  CH2  •  CH  +H20 


NH2      NH2 

\/      +NH2-CH2-CH2.CH2.CH 

C  (Ornithin)  COOH 

-      i 

(Urea) 

A  ferment,  arginase,  found  mainly  in  the  liver,  can 
also  bring  about  this  hydrolysis. 

Lysin  and  arginin  are  called  hexone  bases  (hexone 


AMINO  ACIDS  AND  ACID  AMIDES  271 

refers  to  their  possessing  six  carbon  atoms  in 
the  molecule).  Another  hexone  base  is  histidin, 
CeHgNaC^,  probably  /3-imidazol  a-aminopropionic 
acid, 

CH 

HN      N  NH2 

I         I  I 

CH=C— CH2— CH— COOH. 

It  is  a  heterocyclic  compound  (see  p.  414).  It  is 
now  believed  that  these  hexone  bases  are  present 
in  combination  in  all  protein  molecules.  The 
simplest  proteins,  protamines,  seem  to  contain  prac- 
tically nothing  besides  hexone  bases. 

Another  heterocyclic  compound  derived  from  pro- 
teins is  tryptophan  (see  p.  418),  also  an  a-amino  acid. 

It  seems  advisable  to  mention  in  this  place  two  derivatives 
of  pyrrolidine  (a  heterocyclic  compound,  p.  415)  because  they 
are  obtained,  together  with  the  above  amino  acids,  as  decompo- 
sition products  of  proteins.  They  are  prolin  or  a-pyrrolidine- 
carboxylic  acid, 

CH2 


NH 

and  7-hydroxy-a-pyrrolidine-carboxylic  acid  or  hydroxyprolin. 

Optical  activity  of  the  decomposition  products  of  pro- 
teins: Alanin,  valin,  isoleucin,  glutaminic  acid, 
ornithin,  arginin,  and  lysin  are  dextrorotatory. 
Serin,  leucin,  cystin,  aspartic  acid,  histidin,  phenyl- 
alanin,  tyrosin,  tryptophan,  prolin,  and  hydroxy- 
prolin are  laevorotatory. 


272  ORGANIC  CHEMISTRY 

SULPHUR  DERIVATIVES  OF  AMINO  ACIDS 
Cystein  is  a-amino-0-thiolactic  acid: 

ySH       /NH2 
CH/  —  CH^-—  COOH. 

Two  molecules  combine  to  form  one  molecule  of 
cystin. 


Cystin    has   the  formula  XTTI 

<UCH2-CH/  ' 

.  \COOH 

Cystein  and  cystin  occur  as  decomposition  products  of 
proteins. 

Cystin  crystals  may  occur  in  pathological  urine. 
Reduction  of  cystin  gives  cystein  as  its  product. 

Taurin  is  /3-aminoethylsulphonic  acid, 

/NH2 
CH/—  CH2—  S03H. 

It  is  found  in  bile  combined  with  cholic  acid  as  tauro- 
cholic  acid.  It  has  been  synthesized  from  /3-hydroxy- 
ethylsulphonic  acid  (see  p.  306),  as  indicated  by 
the  following  equations: 

CH2(OH)  •  CH2  •  S03H  +2PC15  = 

=  CH2C1  •  CH2S02C1  +2POC13  +2HC1. 

(Chlorethylsulphon  chloride) 

CH2C1  •  CH2  •  S02C1  +H20  =  CH2C1  -  CH2SO3H  +HCL 

(Chlorethylsulphonic  acid) 

CH2C1  -  CH2  •  S03H  +2NH3  = 

=  CH2NH2  •  CH2  .  S03H  +NH4CL 

(Taurin) 


ACIDS  AND  ACID  AMIDES  273 


ACID  AMIDES 

The  next  group  of  amido  compounds  to  be  con- 
sidered is  that  of  the  acid  amides.     Just  as  there  are 
acid   chlorides,    e.g.,    acetyl   chloride,    CH3-COC1, 
so  there  are  acid  amides,  NH2  occupying  the  position 
of  Cl,  as  acetamide,  CH3-CONH2. 
Acid  amides  may  be  made  in  several  ways: 
(1)  By  treating  an  acid  chloride  with  ammonia: 


CH3  •  COP  +HNH2  =  CH3  •  CONH2  +HC1. 

(2)  By  heating  an  acid  in  an  atmosphere  of  am- 
monia while  constantly  bubbling  dry  ammonia  gas 
into  the  acid: 

CH3  •  CO|OH  +HjNH2  =  CH3  -  CONH2  +H2O. 

(3)  By  treating  an  ester  with  ammonia  : 

COO-C2H5  CO-NH2 

|  +2NH4OH  =  |  +2C2H5OH+2H20. 

COO-C2H5  CO-NH2 

(Diethyloxalate)  (Oxamide) 

(4)  By  heating  the  ammonium  salt  of  the  acid, 
generally  in  a  sealed  tube  (the  process  being  anhy- 
drolysis). 

CH3  •  COONH4  =  CH3  .  CONH2  +H20. 

(Ammonium  acetate)  (Acetamide) 

Acid  amides  are  decomposed  by  the  action  of 
nitrous  acid,  nitrogen  being  liberated.  Amides  are 
hydrolyzed  by  water,  the  action  being  greatly 
accelerated  by  hydrogen  ions.  This  can  be  taken 


274  ORGANIC  CHEMISTRY 

advantage  of  to  determine  hydrion  concentration  of 
solutions  of  different  acids  (p.  172).  The  simpler 
amides,  as  formamide,  conduct  electricity.  Salts 
dissolved  in  these  ionize  somewhat. 

Formamide,  H-CONEb,  is  a  liquid.  The  other 
acid  amides  are  solid  crystalline  substances. 

Acetamide,  CH3-CONH2,  is  prepared  by  the 
fourth  method  given  above  (see  exp.).  It  can  also 
be  prepared  by  the  action  of  ammonium  hydroxide 
on  ethyl  acetate.  It  forms  colorless  crystals,  which 
melt  at  82°  and  distill  at  223°.  It  generally  has  a 
mouse-like  odor,  due  to  slight  admixture  of  impuri- 
ties. It  can  be  purified  by  crystallization  from 
chloroform.  Heating  with  phosphorus  pentoxide 
converts  it  into  methyl  cyanide  (see  p.  255). 

EXPERIMENT.  To  40  gm.  of  glacial  acetic  acid 
heated  in  an  evaporating  dish  to  40-50°  on  a  water 
bath,  add  powdered  ammonium  carbonate  (about 
55  gm.)  while  stirring,  until  a  drop  diluted  with  a 
few  cubic  centimeters  of  water  shows  a  weak  alkaline 
reaction  to  litmus.  Now  heat  to  80-90°  on  a  boiling 
water-bath  until  a  drop  diluted  with  water  shows  a 
slightly  acid  reaction.  Pour  the  mass  while  hot  into 
a  Volhard  tube  or  bomb-tube  through  a  hot  funnel 
(so  as  not  to  smear  the  walls  of  the  tube).  With  a 
strip  of  filter-paper  remove  any  of  the  substance  that 
may  be  adhering  to  the  upper  eight  inches  of  the 
tube. 

Seal  the  tube  carefully.  The  sealing  of  bomb-tubes  requires 
practice.  Experiment  first  with  waste  pieces  of  tubing. 
First  cover  the  tube  with  soot  in  a  smoky  flame  at  the  point 


AMINO  ACIDS  AND  ACID  AMIDES  275 

where  it  is  to  be  sealed.  Increase  the  heat  gradually,  then 
begin  with  a  large  blast  flame.  When  the  soot  is  burned  off, 
decrease  the  size  of  the  flame,  increasing  the  force  of  the  blast. 
Keep  rotating  the  tube,  and  when  it  softens  do  not  draw  it  out, 
but  make  the  tube  sink  in  by  the  force  of  the  blast.  In  this 
way  the  thickness  of  the  wall  is  preserved.  When  the  caliber 
of  the  tube  has  become  very  small,  the  tube  can  be  quickly 
drawn  out  and  sealed  off.  A  tapering  tip  is  the  best.  Heat 
the  tip  in  the  flame  until  rounded.  Keep  the  hot  end  of  the 
tube  in  a  cold  smoky  flame  until  a  deposit  of  soot  is  obtained. 
Let  it  cool  slowly. 

Heat  the  tube  in  a  bomb-furnace  for  five  hours 
at  220-230°.  Open  the  tube  by  making  a  scratch- 
mark  with  a  file  on  the  tip;  wrap  the  tube  in  a 
heavy  towel;  put  the  tip  into  the  blast-flame,  when 
it  will  snap  off.  Sometimes  there  is  a  high  pressure 
of  gases  in  a  bomb-tube,  so  that  it  may  fly  to  pieces 
as  soon  as  the  pressure  is  suddenly  relieved.  Break 
off  the  end  of  the  tube;  remove  the  acetamide  and 
transfer  it  to  a  distilling  flask.  Distill,  reject  the 
distillate  coming  over  below  130°,  then  change  to 
a  wide  tube  (air-condenser)  in  the  place  of  the  Liebig 
condenser.  Collect  the  fraction  distilling  between 
180°  and  230°  in  a  beaker.  Cool  it  with  ice- water 
until  crystals  form;  if  necessary,  scratch  the  wall  of 
the  beaker  with  the  sharp  end  of  a  glass  rod  (see 
p.  8).  Dry  the  crystals  by  pressing  them  on  a 
porous  plate. 

An  easier  method  of  preparation  of  acetamide  is  as 
follows :  Let  a  mixture  of  50  gm.  of  ethyl  acetate  and 
100  c.c.  of  concentrated  ammonium  hydroxide  stand 
for  one  week.  Distill  as  above. 

Glycinamide,  NH2-CH2-CONH2,  the  acid  amide 


276  ORGANIC  CHEMISTRY 

of  glycocoll,  is  of  interest  in  connection  with  the 
biuret  test  (p.  280). 

CONH2 
Oxamide,  is  prepared  by  the  third  method. 

CONH2 

EXPERIMENT.  Connect  two  flasks  with  a  glass 
tube  bent  at  a  right  angle  at  each  end.  In  the  sec- 
ond flask  the  tube  is  long  enough  to  reach  almost  to 
the  bottom.  Into  each  flask  put  50  c.c.  of  alcohol. 
Into  the  second  flask  put  also  50  gm.  of  oxalic  acid 
from  which  the  water  of  crystallization  has  been 
driven  off  by  heating  in  a  oven  at  100°.  The  first 
flask  is  supported  on  wire  gauze,  while  the  second 
is  placed  in  an  oil-bath.  Place  a  thermometer  in  the 
oil.  Connect  the  second  flask  with  a  condenser. 
Heat  the  oil-bath  to  100°,  then  begin  heating  the 
flask  containing  only  alcohol.  While  the  alcohol- 
vapor  is  passing  over,  allow  the  temperature  of  the 
oil-bath  to  rise  slowly  to  125-130°.  When  most  of 
the  alcohol  has  disappeared  from  the  first  flask, 
disconnect  this  flask  and  remove  the  flame.  Cool 
the  second  flask;  the  residue  and  the  distillate 
both  contain  diethyl  oxalate.  Treat  each  with 
strong  ammonium  hydroxide.  A  white  precipitate 
of  oxamide  is  obtained.  Filter  and  wash  the 
precipitate  thoroughly.  Save  a  sample.  Put  some 
oxamide  into  a  test-tube,  add  strong  alkali,  and  boil, 
noting  the  evolution  of  ammonia.  Take  another 
portion  in  a  test-tube,  treat  with  cold  NaOH,  and 
add  very  dilute  copper  sulphate  solution  a  drop  at 
a  time  until  a  reddish  or  violet  color  appears  (biuret 
reaction,  see  p.  282) : 


AMINO  ACIDS  AND  ACID  AMIDES  277 

COOH  COOC2H5 

|  +2C2H5OH=|  +2H20, 

COOH  COOC2H5 

COOC2H5  CONH2 

+2NH4OH=  |.  +2C2H5OH+2H20. 

COOC2H5  CONH2 

Asparagin  is  the  mono-amide  of  aspartic  acid,  its 

CH2—  CONH2 
formula  being  |  .     It  occurs  as  both 

CH(NH2)—  COOH 

the  dextro  and  the  ISBVO  variety  ;  the  commoner  kind 
(Isevo)  is  tasteless  while  the  dextro  tastes  sweet.  It 
is  found  in  many  vegetables,  particularly  asparagus, 
peas,  beans,  beets,  and  wheat. 

Glutamin  is  the  mono-amide  of  glutaminic  acid, 
having  the  formula 

/NH2 
CH^-  -COOH 

CH2  --  CONH2* 

The  most  important  acid  amide  of  all  is  carbamide. 
Urea  (carbamide),  NH2-CONH2,  is  the  acid  amide 
of  carbamic  acid.  It  is  also  the  diamide  of  carbonic 
acid: 

/OH  /NH2 

o=c<       ->  o=c< 

XOH  XNH2 

The  relationship  of  urea  to  carbamic  acid  is  shown  by 
its  preparation  from  ammonium  carbamate  by  heat- 
ing in  a  sealed  tube  at  a  temperature  of  135°: 

XNH2  /NH2 

O=C<  =0=C<         +H20. 

XONH4  XNH2 

(Ammouium  carbamate)  (Urea) 


H2\ 


278  ORGANIC  CHEMISTRY 

Its  relationship  to  carbonic  acid  is  evidenced  by  its 
production  from  carbonyl  chloride  and  ammonia: 

/Cl  /NH2 

0=C<     +2NH3=0=C<          +2HC1, 
XC1  XNH2 

(Carbonyl  chloride) 

also  from  ethyl  carbonate  and  ammonia: 

/OC2H5  /NH2 

O=C<  +2NH3  =  0=(\         +2C2H5OH. 

XOC2H5  XNH2 

(Ethyl  carbonate) 

That  it  bears  a  relationship  to  cyanic  acid,  HCNO, 
and  its  amide  cyanamide,  N=C — NH2,  is  proved  by 
its  preparation  from  both  of  these.  By  hydrolysis 
cyanamide  is  converted  into  urea: 

CN-NH2+H20=0=C/       2. 

\JNJbi2 

Mere  evaporation  of  a  solution  of  ammonium  iso- 
cyanate  is  sufficient  to  convert  the  salt  into  urea 
(see  exp.) ;  this  involves  intramolecular  change: 

XT— NH4  /NH2 


\NH2 

(Ammonium  iso-cyanate) 

The  change  of  cyanate  to  urea  is  a  reversible 
reaction.  A  decinormal  solution  of  ammonium 
isocyanate  changes  on  standing  until  it  reaches  an 
equilibrium  point,  at  which  95%  of  the  cyanate  has 
become  urea.  On  the  other  hand  a  urea  solution 
changes  until  it  reaches  the  same  equilibrium  point, 
i.e.,  when  5%  has  been  changed  to  cyanate. 


AMINO  ACIDS  AND  ACID  AMIDES  279 

Physiologists  have  advocated  three  main  hypotheses  as  to 
the  origin  of  urea  in  the  animal  body,  corresponding  to  the 
above  methods  of  synthesis,  namely,  that  it  is  derived  from 
(1)  ammonium  carbonate,  (2)  from  ammonium  carbamate, 
or  (3)  from  ammonium  cyanate.  It  seems  most  likely  that 
the  derivation  of  urea  is  as  follows  :  Ammonia  enters  the  blood 
of  the  portal  venous  system  mainly  as  the  result  of  fermentative 
and  bacterial  hydrolysis  of  the  proteins  of  the  food.  In  the  pres- 
ence of  the  large  amount  of  carbonic  acid  in  the  blood,  am- 
monium carbonate  and  carbamate  are  formed  in  accordance 
with  the  laws  of  mass  action;  both  of  these  are  then  converted 
in  the  liver  into  urea  by  a  process  of  anhydrolysis: 

ONH4  /NH2  /NH2 

- 


0=C<          (  -  H20)  ->  0=  C  (  -  H20) 

\ONH4  \ONH4  XNH2 

(Ammonium  carbonate)  (Ammonium  carbamate)  (Urea) 

A  certain  portion  of  the  amino  acids  which  are  not  used  by 
the  tissues  for  synthesis  of  proteins  probably  become  a  source 
of  urea  in  the  following  manner:  The  monoamino-acids  may 
be  acted  on  by  ferments  (deamidization)  so  that  ammonia  is 
split  off  (the  presence  of  ferments  possessing  that  power  has 
been  demonstrated  in  many  organs),  and  then  the  ammonia 
becomes  ammonium  carbonate  and  carbamate,  and  is  changed 
to  urea.  Arginin  may  be  hydrolyzed  by  a  ferment,  arginase, 
which  is  present  in  many  organs,  urea  being  one  of  the  products 
(see  p.  270). 

Urine  contains  a  large  quantity  of  urea,  20  to 
30  gm.  of  urea  being  excreted  in  the  urine  of  man  in 
twenty-four  hours  on  a  mixed  diet.  It  crystallizes 
in  colorless  needles  or  rhombic  prisms.  It  melts 
at  132°  (corrected  melting-point  is  132.6°).  It  is 
very  soluble  in  water  and  hot  alcohol,  less  soluble  in 
cold  alcohol. 

Bacterial  fermentation  of  urine  converts  urea  into 


280  ORGANIC  CHEMISTRY 

ammonium  carbonate,  hence  the  ammoniacal  odor 
of  decomposed  urine.  An  enzyme  urease,  also  boil- 
ing with  alkalies  or  acids  or  superheating  with  water, 
can  accomplish  a  similar  hydrolysis: 


/2     (2       NH4\ 
C0<         +          =         >C03. 
X 


Of  course  by  the  action  of  alkali  NH3  is  liberated 
from  the  (NH4)2CO3,  while  by  the  action  of  acid 
CO2  is  liberated.  This  reaction  is  the  basis  of 
Bunsen's  and  Folin's  methods  of  quantitative 
estimation  of  urea.  The  most  satisfactory  method 
of  estimation  is  that  in  which  urease  is  used.  Sodium 
hypochlorite  and  hypobromite  decompose  urea, 
liberating  nitrogen; 

CO(NH2)2  +3NaBrO  =  N2  +3NaBr  +C02  +2H20. 

This  reaction  is  made  use  of  in  the  usual  clinical 
method  for  urea  estimation.  Nitrous  acid  also 
liberates  free  nitrogen  (see  p.  260)  : 

CO(NH2)2  +2HN02  =2N2  +CO2  +3H20. 

When  heated  strongly,  urea  yields,  among  other 
substances,  biuret,  NH2-CO-NH-CO-NH2,  which 
gives  a  reddish-violet  color  reaction  with  caustic 
soda  or  potash  containing  a  trace  of  copper  sulphate 
(biuret  reaction).  This  reaction  is  given  by  oxam- 
ide,  in  fact  by  all  substances  containing  two  groups 
of  CO-NH2  linked  together  either  directly  (as  in 
oxamide)  or  through  a  single  nitrogen  (as  in  biuret) 


AMWO  ACIDS  AND  ACID  AMIDES  281 

/  /CONH2\ 

or  carbon  atomf  as  in  CTb,  \  )  or  through  one 

\  \COJN  xi2/ 

/  CO-CONH2\ 

or  more  CO-NH  groups  I  as  in     I  ). 

\          NH-CONH2/ 

CH2-NH2  may  take  the  place  of  one  of  the 
CONEb  groups,  as  in  glycinamide  (p.  275).  All 
proteins  give  the  biuret  reaction  (p.  296) . 

Urea  acts  as  a  weak  monacid  base  toward  certain 
acids,  the  nitrate  and  oxalate  being  particularly 
characteristic  salts.  In  the  common  method  for 
extraction  of  urea  from  urine,  it  is  precipitated  from 
the  urine  (previously  concentrated  by  evaporation) 
by  treatment  with  nitric  acid.  The  urea  is  liberated 
from  the  nitrate  by  treating  the  latter  with  barium 
carbonate, 

EXPERIMENT.  (1)  Synthesize  urea  as  follows: 
Heat  25  gm.  of  powdered  potassium  cyanide  in  an 
iron  dish  until  it  begins  to  fuse  (do  this  under  a 
hood),  then  add  gradually  70  gm.  of  red  oxide  of 
lead  a  little  at  a  time,  stirring  in  well.  When  the 
frothing  ceases  pour  on  an  iron  plate.  When  it  is 
cool  powder  the  mass,  separating  out  the  metallic 
lead.  Digest  this  crude  cyanate  for  an  hour  with 
100  c.c.  of  cool  water.  Filter  through  a  plaited  fil- 
ter into  an  evaporating  dish.  Add  to  the  filtrate  25 
gm.  of  ammonium  sulphate  that  has  been  dissolved 
in  a  small  quantity  of  water.  Evaporate  to  dryness 
on  a  water-bath,  stirring  frequently  to  prevent  crust- 
ing over.  Cool  the  residue  and  powder  it  in  a  mor- 
tar. Transfer  it  to  a  small  flask,  add  100  c.c.  of 


282  ORGANIC  CHEMISTRY 

alcohol,  attach  to  a  reflux  condenser,  and  boil 
for  fifteen  minutes.  Filter  off  the  hot  alcohol  into 
an  evaporating  dish.  Use  25  c.c.  more  of  alcohol 
in  a  similar  manner.  Evaporate  the  alcohol  on 
a  water-bath  to  very  small  bulk.  When  it  is  cool, 
urea  crystals  should  form.  Test  a  few  crystals  or 
some  of  the  solution  as  below. 

(2)  Urea  tests,  (a)  Put  one  drop  of  concentrated 
urea  solution  on  a  glass  slide;  mix  with  it  one  drop 
of  colorless  concentrated  nitric  acid.  Place  a  cover- 
glass  over  the  crystals  and  examine  under  a  micro- 
scope. 

(6)  In  a  test-tube  melt  some  dry  urea,  then  heat 
gently  for  a  minute  while  gas  (NHa)  is  being  evolved. 
Cool;  add  1  c.c.  of  water,  then  an  equal  amount  of 
20%  NaOH  solution,  and  finally  a  small  drop  of 
very  dilute  copper  sulphate  solution.  A  violet  or 
pinkish  color  is  obtained.  This  is  called  the  biuret 
reaction  (see  above)  : 

NH2     NH2 

oc/      +       \co= 

X  X 


(Urea)  ......  "(Urea) 

=NH2—  CO—  NH—  CO-NH2  +NH3. 

(Biuret) 

If  the  heating  has  been  continued  beyond  a  cer- 
tain point,  an  insoluble  compound,  cyanuric  acid, 
(HCNO)3,  is  formed;  this  results  from  the  combina- 
tion of  one  molecule  of  biuret  with  one  of  urea, 
2NHs  being  eliminated. 

Veronal  is  a  urea  derivative,  being  diethylmalonyl- 
urea  or  diethylbarbituric  acid, 


AMINO  ACIDS  AND  ACID  AMIDES  283 

C2H5          CO— 


V 
>CO. 


This  is  used  as  a  hypnotic.  The  sodium  salt  of 
veronal  is  also  used  for  the  same  purpose. 

Another  hypnotic  related  to  urea  is  hedonal,  which 
is  really  a  carbamate  similar  to  urethane.  Hedonal 
is  methylpropylcarbinolurethane : 

/NH2 

C0<  /CH3 

^0—CR<( 

^C3R7 

Bromural  is  another  hypnotic,  derived  from  urea. 
It  is  monobrom-iso-valeryl-urea, 

CH3  -  CH  -  CHBr  •  CO— NH  -  CO  -  NH2. 

CH3 

Neuronal  is  a  hypnotic,  having  a  somewhat 
similar  structure,  CBr(C2H5)2CONH2. 


CHAPTER  XX 

ACID  IMIDES.    COMPLEX  AMINO  AND  IMIDO  COM- 
POUNDS, INCLUDING  POLYPEPTIDES 

ACID  IMIDES 

THESE   contain    the   group   NH,   illustrated   by 

CH2— C(X 
succinimide,     |  >NH.     They    are    formed 

CH2— CCr 

from  acid  amides  by  loss  of  ammonia,  the  amide  of 
a  dibasic  acid  being  necessary: 


\ 


CH2-CONH2    CH2-CO 
I  =  |  >NH+NH3. 

CH2-CONH2    CH2-COX 

(Succinamide)  (Succinimide) 

OTHER  AMINO  AND  IMIDO  COMPOUNDS 

/NH2 

Guanidin,  NH=C^         ,  may  be  considered  as  an 
\NH2 

imido  derivative  of  urea,  and  might  be  called  imido- 
carbamide.  It  can  be  synthesized  from  cyanamide 
and  ammonia: 

/NH2 
CN-NH2+NH3=NH=C<T       . 

(Cyanamide)  \NH2 

(Guanidin) 

It  is  more  strongly  basic  than  urea,  undoubtedly 
because  of  the  changing  of  the  carbonyl  linking  of 

284 


AMINO  AND  IMIDO  COMPOUNDS  285 

urea  for  the  naturally  basic  NH  group.    Methyl- 

/NH2 
guanidin,  HN=C<T  ,TTT/~TT  N,  occurs  as  a  ptomaine 


(p.  263).     Of  more  importance  are  the  derivatives 
of  guanidin,  namely,  creatin  and  creatinin. 
Creatin  is  methylguanidinacetic  acid, 

NH2     /CH3 


COOH. 

Creatin  can  be  synthesized  from  cyanamide  and 
sarcosin: 

/NH—  CH3_ 
CN  •  NH2  +CH/—  COOH 

(Cyanamide)  (Sarcosin) 


X3H2—  COOH. 

Creatin  is  present  in  considerable  quantity  in  mus- 
cular tissue.  It  can  be  obtained  from  meat  extract. 
Heating  with  baryta  water  converts  it  into  urea, 
sarcosin,  and  some  other  substances.  Heating  with 
dilute  acid  changes  it  to  creatinin.  As  a  rule  the 
appearance  of  creatin  in  the  urine  is  pathological, 
though  it  is  reported  as  occurring  normally  in  the 
urine  of  children. 

Creatinin  is  creatin  less  a  molecule  of  water: 

/NH  -  CO 
NH=C<      /CH3  |     . 
^N^~    -CH2 

This  is  always  present  in  normal  human  urine,  about 
1.5  gm.  being  excreted  in  twenty-four  hours.  The 


286  ORGANIC  CHEMISTRY 

amount  excreted  when  creatinin-containing  food 
(flesh)  is  debarred  from  the  diet  seems  to  be  a 
fixed  quantity  for  each  individual,  no  matter  how 
much  the  total  nitrogen  content  of  the  urine  may 
vary. 

Creatinin  crystallizes  in  monoclinic  prisms.  It  is 
readily  soluble.  In  alkaline  solution  it  becomes 
converted,  at  least  in  part,  into  creatin.  It  reduces 
Fehling's  and  other  alkaline  copper  solutions,  but 
it  holds  cuprous  oxide  in  solution;  on  account  of 
these  properties  it  may  mislead  in  testing  for  sugar 
if  the  urine  is  concentrated.  An  alkaline  bismuth 
solution,  however,  is  not  reduced  by  creatinin. 
Creatinin  is  precipitated  by  mercuric  chloride  and 
by  zinc  chloride,  these  reagents  entering  into  chem- 
ical union  with  the  creatinin. 

Uric  acid  is  a  derivative  of  urea.  In  uric  acid  two 
molecules  of  urea  unite  by  linking  to  an  inter- 
mediate carbon  chain,  each  NH2  group  losing  one 
hydrogen  atom  and  becoming  NH  in  order  to  effect 
the  union: 


,NH— 
NH— 

C 

1 
C 

1 
C 

—  HNV 
>C=0. 
—H.W 

This  is  the  skeleton  of  the  uric  acid  formula.  The 
presence  of  two  urea  molecules  and  of  a  carbon  chain 
is  shown  by  the  nature  of  the  decomposition  prod- 
ucts of  uric  acid  resulting  from  oxidation  and  hydrol- 
ysis: 


AMINO  AND  IMIDO  COMPOUNDS 


287 


NH— CO 

I.  CO     C— NHV 

||  >CO+H20+0 

[— C— NHX 


NH- 

(Uric  acid)  [treated  with  cold  HNO3] 


NH— CO 

I          I        NH 


2\ 


II. 


=  CO     CO  +         >CO. 
|          |        NH/ 
NH—  CO 

(Alloxan)               (Urea) 

NH—  C 
CO     ( 
NH—  C 

(Alloxan)  [trea 
warm  t 

^0 

X>+0     = 

:o 

ted  with 
[NOs] 

NH—  CO 
CO           +CO2. 
NH—  CO 

(Parabanic  acid) 

NH—  ( 

1 

:o 

NH—  ( 

1 

^O 

CO 

1 

+H20 

=     CO 

1 

NH—  ( 

banic  acid)  [tr 

:o 

3ated  with  alkali] 

NH2  ( 

(Oxah 

^OOH. 

iric  acid) 

III. 


NH— CO 
IV.  CO 


+H20     = 


NH2  COOH 

(Oxaluric  acid)  [boiled  with  water] 


NH2    COOH 

+| 
NH2    COOH. 

(Urea)       (Oxalic  acid) 

N— C 


The  presence  of  the  pyrimidin  ring,  C     C,  in  uric 

N— C 

acid  is  shown  by  Traube's  synthesis,  which  is  as  fol- 
lows:   Cyanacetic  acid  and  urea  are  treated  with 


288  ORGANIC  CHEMISTRY 

POC13;   the  latter  removes  hydroxyl  from  the  acid, 
and  urea  takes  its  place  to  form  cyanacetyl  urea: 

/CN 
(1)  CH2.COOH+NH2-CO-NH2  = 

(Cyanacetic  acid)  (Urea) 

CH2—  CN 


+H20. 

NH—  C—  NH2 

II 
O 

(Cyanacetyl  urea) 

Treating  cyanacetyl  urea  with  alkali  causes  a  shifting 
within  the  molecule,  resulting  in  the  formation  of 
monoamino-dioxy-pyrimidin, 

HN—  C=O 


(2)  0=C    CH2     . 

HN—  C=NH 

This  is  treated  with  HNO2,  giving 
HN—  C=O 

(3)  o=C    C=NOH. 

I      I 
HN—  C—  NH 

By  reduction  this  becomes 

HN—  C—  O 

0=C     C—  NH2, 

I      II 
HN—  C—  NH2. 


AMINO  AND  IMIDO  COMPOUNDS  289 

which  when  acted  on  by  CC100C2H5+KOH  gives 

(Ethyl  chlorcarbonate) 

HN—  C=O 

(4)  o=C     C—  NK—  COOC2H5, 
HN—  C—  NH2 

a  pyrimidin  derivative  of  urethane.  By  heating  this 
potassium  salt  (dry)  to  150°,  then  later  to  180°- 
190°,  alcohol  is  split  off,  leaving  uric  acid  (as  potas- 
sium urate)  : 

HN—  CO 


(5)  o—  C     C—  NKX 

|      ||  >C=0+C2H5OH. 

HN—  C—  NIT 

This  synthesis  conclusively  proves  the  structure  of 
uric  acid. 

Another  interesting  synthesis,  because  it  is  anal- 
ogous to  one  which  may  occur  in  the  animal  body, 
(at  least  in  birds),  is  effected  by  heating  together 
urea  and  trichlorlactamide  : 

H)—  NH         CO—  (NH2) 

CO  C—  (HOH)  NHV(H) 

\  I  >co 

(H)—  NH          C—  (C13)  NH^(H) 

(Urea)  (Trichlorlactamide)  (Urea) 

The  groups  in  parenthesis  do  not  enter  into  the  uric 
acid  molecule,  but  unite  to  form  NH4C1,  HC1,  and 
H20. 


290  ORGANIC  CHEMISTRY 

/NH— COv 

Dialuric  acid,  COC  >CHOH,  appears  in 

\N  H — O  O' 

the  case  of  birds  to  be  an  intermediate  body  in  the 
synthesis  of  uric  acid  by  the  liver.  It  is  formed  by 
the  combination  of  urea  with  tartronic  acid  (p.  221). 
By  the  addition  of  another  urea  molecule  to  this, 
uric  acid  is  produced: 


(HOH)+NH^(H) 


VNH— C(O) 

(Dialuric  acid)  (Urea) 

NH— CO 


=  CO     C— NHX 

>CO  +  2H20. 


NH— C— NIT 

(Uric  acid) 

Analogous  synthesis  in  the  case  of  mammals 
has  not  been  proved. 

Uric  acid  has  been  synthesized  by  heating  together 
glycocoll  and  urea.  On  the  other  hand,  uric  acid  when 
heated  in  a  sealed  tube  with  HC1  yields  glycocoll. 

Tautomerism  of  uric  acid.  Uric  acid  exists  not 
only  in  the  form  corresponding  to  the  above  formula 
(the  lactam  state)  but  also  in  another  form  (the  lactim 
state),  in  which  the  three  0  atoms  are  in  hydroxyls: 

N=C— OH 

i       I 
HO— C     C— NH 


AMINO  AND  IMIDO  COMPOUNDS  291 

The  lactam  form  is  less  stable.     It  is  stated  that  in 
the  urine  uric  acid  is  in  the  lactim  form. 

Uric  acid  acts  as  a  weak  dibasic  acid,  forming 
urates.  It  does  not,  however,  play  any  part  in  the 
acid  reaction  of  urine.  It  is  believed  to  exist  mainly 
in  the  form  of  monosodium  urate  in  both  the  blood 
and  the  urine.  In  very  acid  urine  there  is  some  free 
uric  acid.  It  often  crystallizes  out  as  a  reddish 
deposit  from  strongly  acid  urine.  About  0.7  gm. 
is  excreted  daily  by  man.  Pure  uric  acid  is  a  color- 
less crystalline  powder.  It  is  almost  insoluble  in  cold 
water  and  alcohol.  Uric  acid  reduces  Fehling's  solu- 
tion, but  does  not  reduce  an  alkaline  bismuth  solution. 

EXPERIMENT.  (1)  Add  5  c.c.  of  20%  HNO3  to  a 
little  uric  acid  in  an  evaporating-dish ;  evaporate  to 
dry  ness  on  a  water-bath.  Alloxantin  is  formed. 
To  the  residue  add  baryta  water;  a  blue  color 
appears. 

(2)  Repeat  the  above,  but  instead  of  using  baryta 
expose  the  residue  to  fumes  of  ammonia.  A  red 
color  is  obtained,  due  to  murexide.  This  test  is 
called  the  murexide  test.  If  much  ammonia  is 
present  in  the  air,  the  residue  will  be  reddish  because 
of  the  ammonia  taken  up.  Ammonia  converts 
alloxantin  into  purpuric  acid, 

HN— CO  NH  OC— NH 

OC     C/ \C    CO. 

II  II 

HN— CO         OC— NH 

Murexide  is  the  ammonium  salt  of  this  acid. 


292  ORGANIC  CHEMISTRY 

/NH— CH— NIL 
Allantoin,    CO  >CO,  results   from 

\NH-CO  NH2X 

careful  oxidation  of  uric  acid  by  potassium  per- 
manganate. It  occurs  in  the  urine  of  calves  and 
dogs,  and  at  times  in  human  urine. 

Purin  bodies.     Uric  acid  and  all  the  purin  bodies 
contain  the  double-ring  nucleus 

N— C 

C     C— Nv 

i       i         \r* 
/O. 

N— C— W 


The  main  ring  is  the  pyrimidin  ring;  the  purin 
nucleus,  therefore,  is  pyrimidin  with  urea  attached 
as  a  secondary  ring.1  The  relationship  of  the  purin 
bodies  is  shown  below: 

Purin  itself  has  an  H  atom  at  each  of  the  positions 
numbered  2,  6,  7,  and  8.  It  can  be  prepared  from 
uric  acid. 

(1)  N— C  (6)  NH— CO 

II  II 

(2)  C     C  (5)—  N(7)v  CH     C— NHV 

>C(8)      ||         ||  >CH 


(3)  N—  C  (4)—  N(9) 


(Purin  nucleus)  (Hypoxanthin) 

(6-oxypurin) 

1  The  purins  and  pyrimidins  are  heterocyclic.  We  prefer 
to  discuss  the  chemistry  of  them  at  this  point  because  of  their 
relationship  to  urea  and  proteins.  They  show  no  similarity  to 
the  typical  heterocyclic  compounds. 


AM  I  NO  AND  I  MI  DO  COMPOUNDS  293 

NH— CO  NH— CO 

CO     C— NIL  CO     C— N(CH3) 

I         II  >CH  \OH 

NH-C W  ./CH 

•(CHs)N C— N 

(Xanthin  (Theobromine,  dimethylxanthin) 

(2,  6-dioxypurin)  (3,  7-dimethyl-2,  6-dioxypurin) 

(CH3)N— CO 

I       I         /(CH8) 
CO  C— W 


H 

I— (J— IT 


(CHs)N- 

(Caffeine,  theine,  trimethylxanthin)  (1,  3,  7-trimethyl-2,  6-dioxypurin) 


NH— CO 
CO     C— NIL 

I       II       >co 

NH— C— NHX 

(Uric  acid)  (2,  6,  8-trioxypurin) 


CH     C— NH  H2N— C        C— NH 


N=C— NH2  NH— CO 

>AJ.2J-1 V>                 O Ix  J-J-v 
CH                   ||        ||          >CH 
IN v IN  -                          N C W 

(Adenin)  (Guanin) 

(6-aminopurin)  (2-amino-6-oxypurin) 

There  are  a  number  of  methyl  purins  besides 
caffeine  and  theobromine,  as,  1  methyl  xanthin, 
7  methyl  xanthin  (heteroxanthin) ,  1,  7  dimethyl 
xanthin  (paraxanthin),  and  7  methyl  guanin. 

The  purins  are  also  called  alloxuric,  xanthin,  or 
nuclein  bodies. 

Caffeine  and  theobromine  when  taken  as  food  are 
excreted  in  the  urine  partly  unchanged  and  partly 


294  ORGANIC  CHEMISTRY 

as  monomethyl  and  dimethyl  xanthins.  Only  35- 
40%  of  caffeine  and  theobromine  appear  in  the 
urine  as  purine  bodies.  A  number  of  investigators 
agree  in  the  assertion  that  tea  and  coffee  do  not 
increase  uric  acid  excretion.  The  other  purins 
are  excreted  mainly  as  uric  acid.  It  is  believed  by 
some  that  on  a  diet  that  is  free  of  purin  bodies,  the 
amount  of  purins  excreted  daily  is  a  fixed  quantity 
for  each  individual  (cf.  creatinin).  In  the  case  of 
mammals  the  purin  bodies  have  their  origin  in  the 
nucleic  acids  of  nucleoproteins,  both  those  of  the 
tissues  and  those  of  the  food. 

Some  of  the  purins,  mainly  xanthin  and  hypo- 
xanthin,  are  found  in  muscle,  and  therefore  in  meat 
extract.  Beef  tea  or  a  solution  o  meat  extract 
contains  as  its  organic  constituents  chiefly  creatin, 
purin  bodies,  and  sarcolactic  acid. 

Theobromine  (dimethylxanthin)  is  found  in  choc- 
olate and  cocoa.  It  is  called  an  alkaloid  (see 
p.  425). 

Caffeine  or  theine  (trimethylxanthin)  is  the  alka- 
loidal  principle  in  tea  and  coffee  Both  theobromine 
and  caffeine  are  used  as  medicines. 

EXPERIMENT.  Try  the  murexide  test  (see  p.  291) 
on  a  little  caffeine.  Repeat,  substituting  bromine 
water  for  HNOs. 

Pyrimidin  derivatives.  These  are  derived  from 
nucleic  acid  by  hydrolysis  whether  by  the  action  of 
acids  or  by  post-mortem  autolysis  of  animal  tissue. 

The  most  important  are  uracil,  thyrnin  and 
cytosin. 


AMINO  AND  IMIDO  COMPOUNDS  295 

Uracil  is  2,  6  dioxypyrimidin, 

NH— C= 0 

I          I 
O=C       CH. 


Thymin  is  5  methyl  2,  6  dioxypyrimidin, 
NH— C=0 

O=C       C— CH3. 

I         II 
NH— CH 

Cytosin  is  6  amino  2  oxypyrimidin, 
N=C— NH2 
0— C        CH 

NH— CH 

As  an  illustration  of  a  nucleic  acid  might  be  men- 
tioned one  which  has  been  obtained  from  a  nucleo- 
protein  of  the  thymus  gland.  It  is  believed  to 
consist  of  the  linking  together  of  four  hexose  (p.  231) 
and  four  phosphoric  acid  molecules  with  one  mole- 
cule each  of  guanin,  adenin,  thymin  and  cytosin. 
To  it  has  been  assigned  the  formula : 


Leucomaine  is  a  term  applied  to  basic  substances 
found  in  living  animal  tissues.  The  purin  bodies 
and  the  creatinin  group  of  compounds  are  the  chief 
leucomaines. 


296  ORGANIC  CHEMISTRY 

DIPEPTIDES  AND  POLYPEPTIDES 

Because  of  the  fact  that  the  decomposition  prod- 
ucts of  proteins  include  amino-acids  (as  alanin, 
glycocoll,  leucin,  tyrosin,  aspartic  acid,  etc.)  and  the 
hexone  bases,  it  has  been  proposed  to  explain  the 
structure  of  the  protein  molecule  as  a  chaining  to- 
gether of  these  amino  bodies  by  means  of  the  removal 
of  OH  of  a  carboxyl  group  of  the  one  amino  body  and 
an  H  of  the  amino  group  of  another  (cf.  formation 
of  acid  amides),  thus: 


/!OH     HI 
NH2  •  CH2  -  CO"-  -NH  •  CH2  •  COOH;       ; 

(Glycylglycin) 

or  a  more  complicated  chain,  as: 

-NH  •  CH  •  CO-NH  •  CH  -  CO-NH  CH  CO-hNH— 


C-iHg  CH2' 


[2-COOH    C3H6-CH2-NH2 

(Leucin)  (Aspartic  acid)  (Lysin) 

Of  course  the  above  is  supposed  to  be  only  a  part 
of  the  formula. 

This  theory  of  the  constitution  of  protein  mole- 
cules gives  the  best  explanation  of  the  universality 
of  the  biuret  test  as  applied  to  proteins  (see  p.  281) 
the  test  being  due  to  the  many  CONH  groups. 

On  the  basis  of  this  hypothesis  the  problem  of  the 
synthesis  of  protein  is  now  being  vigorously  attacked. 
Compounds  have  been  synthesized  in  which  two, 
three,  and  even  up  to  eighteen  molecules  have  been 
made  to  combine  in  this  manner;  these  synthetic 
bodies  are  called  pep  tides. 


AMINO  AND  IMIDO  COMPOUNDS  297 

If  two  molecules  have  united,  the  compound  is  a 
dipeptide;  for  example,  glycylglycin, 

NH2  -  CH2  •  CO— NH  -  CH2  •  COOH. 

Polypeptides  are  built  up  from  more  than  two  mole- 
cules;   they  include  tripep tides  (as  diglycylglycin, 

NH2  •  CH2  •  CO— NH  •  CH2CO— NH  •  CH2  •  COOH), 

tetrapeptides,  pentapeptides,  hexapep tides,  etc. 

A  polypeptide  composed  of  three  leucin  and 
fifteen  glycocoll  molecules  has  been  synthesized,  the 
formula  being  CdsHgoOigNis  and  the  molecular 
weight  1213. 

Certain  polypeptides,  identical  with  those  pro- 
duced synthetically,  have  been  obtained  by  partial 
hydrolysis  of  proteins.  The  more  complex  poly- 
peptides show  certain  resemblances  to  peptones  in 
their  actions.  They  taste  bitter.  They  are  pre- 
cipitated by  the  same  reagents,  and  give  the  biuret 
test.  Those  that  are  composed  of  amino  acids  of  the 
same  optical  activity  as  those  occurring  in  proteins 
are  hydrolyzed  by  trypsin.  Their  solutions  are 
colloidal. 

E.  Fischer,  who  is  doing  such  brilliant  work  in 
this  line  of  synthesis,  is  inclined  to  doubt  whether 
this  comparatively  simple  method  of  linking  is  the 
only  kind  of  linking  existing  in  protein  molecules. 

PROTEINS 

Proteins  are  complex  nitrogenous  compounds  that 
yield  on  complete  hydrolysis  mainly  amino  acids, 
hexone  bases  (p.  270),  and  ammonia.  They  vary 


298  ORGANIC  CHEMISTRY 

widely  in  the  proportion  of  the  different  amino  acids 
and  bases  contained  in  their  molecules;  e.g.,  haemo- 
globin has  not  less  than  20%  of  leucin,  but  gelatin 
only  about  2%;  on  the  other  hand  there  is  16.5  per 
cent  of  glycocoll  in  gelatin  and  none  in  haemoglobin. 
Gelatin  has  very  little  of  aromatic  amino  acids. 
Tryptophan  seems  to  be  the  amino  acid  of  proteins 
which  is  most  essential  to  proper  nourishment. 
Most  proteins  contain  S  (cystin),  some  P.  Since 
they  form  colloidal  solutions,  molecular  weight 
determination  has  not  been  successful.  The  lowest 
possible  molecular  weight  of  haemoglobin  is  over 
16,000,  calculating  on  the  basis  of  the  percentage 
composition,  and  supposing  that  there  is  one  atom 
of  iron  in  the  molecule;  this  corresponds  to  the 
formula  : 


The  most  important  classes  of  proteins  are  pro- 
tamines,  histones,  albumins,  globulins,  phospho- 
proteins,  scleroproteins,  compound  proteins  (chro- 
moproteins,  glucoproteins  and  nucleoproteins), 
derived  proteins  (coagulated  proteins,  acid  and 
alkali  metaproteins,  proteoses  and  peptones),  and 
certain  classes  of  vegetable  proteins  called  glutelins 
and  prolamines  (or  gliadins). 

lodothyrin  (thyroiodin)  is  the  iodin-containing 
portion  of  the  compound  protein,  thyreoglobulin, 
present  in  thyroid  tissue. 

Oxyproteic  acid,  C43H82Ni4O3iS,  is  a  derivative  of 
protein.  It  is  found  in  the  urine,  and  may  be  greatly 
increased  in  some  pathological  conditions. 


CHAPTER  XXI 

UNSATURATED  HYDROCARBONS  AND  THEIR 
DERIVATIVES 

THE  most  important  unsaturated  hydrocarbons 
are  the  ethylenes  and  acetylenes.  Their  unsaturation 
consists  in  having  two  or  three  bonds  or  linkings 
between  one  or  more  pairs  of  carbon  atoms,  thus: 

0=C,  C=C,  0= C— 0= C,  C=C=C,  etc. 

The  unsaturation  is  undoubtedly  not  of  so  simple 
a  nature  as  is  indicated  by  the  double  and  triple 
bond.  Unsaturated  substances  of  this  nature  readily 
form  addition  compounds,  as  with  iodine  and 
bromine.  This  fact  is  taken  advantage  of  in 
analysis  of  fats  and  oils,  the  estimation  of  the  oleic 
and  other  unsaturated  acids  being  made  by  the  use 
of  an  iodine  solution  (see  p.  206). 

Another  illustration  of  the  formation  of  addition 
compounds  is  the  production  of  ethylene  bromide, 
C2H4+Br2=C2H4Br2.  Halogen  acids  (HBr,  HI) 
are  added  to  these  hydrocarbons  in  similar  manner: 
C2H4+HBr  =C2H5Br.  The  addition  compound  is, 
of  course,  saturated. 

That  the  place  of  double  linking  is  a  weak  point 
in  the  chain  is  shown  by  the  fact  that  vigorous 
oxidation  results  in  rupture  of  the  C  chain  at  this 
point. 

299 


300  ORGANIC  CHEMISTRY 


ETHYLENES 

Ethylenes  or  olefins,  CnH2n,  form  an  homologous 
series. 

Ethylene  (ethene,  olefiant  gas),  CH2=CH2,  is  the 
only  member  of  importance,  and  is  contained  in 
coal  gas  (about  2%).  It  is  colorless  and  burns 
with  a  yellow  flame.  Ethylene  forms  an  explosive 
mixture  with  oxygen.  It  is  obtained  by  decom- 
position of  ethyl  sulphuric  acid  by  heat,  C2H5HSO4 


EXPERIMENTS.  (1)  In  a  liter  flask  heat  a  mixture 
of  30  c.c.  of  alcohol  and  83  c.c.  of  C.P.  H2SO4  (it  is 
stated  that  HsPCU  can  be  used  instead  of  H2SO4, 
avoiding  the  carbonizing),  using  a  sand-bath.  Put 
a  little  sand  in  the  flask.  Use  a  three-holed  cork. 
It  is  best  to  use  rubber  stoppers  for  the  entire 
apparatus  because  of  the  pressure  of  gas  that  is 
obtained.  Insert  a  dropping  funnel,  also  a  ther- 
mometer placed  so  that  the  bulb  is  immersed  in  the 
liquid.  Connect  with  a  series  of  wash-bottles  as 
shown  in  the  diagram;  the  first  bottle  having  H2SO4, 
the  Woulff  bottle  (having  a  safety-tube)  containing 
dilute  NaOH  solution,  and  each  of  the  last  bottles 
having  a  mixture  of  10  c.c.  of  bromine  and  10  c.c. 
of  water.  A  loosely  corked  flask  partly  filled  with 
dilute  alkali  catches  any  bromine  vapor  that  may 
pass  over.  Begin  heating  the  flask,  and  when  the 
temperature  reaches  170-175°  this  is  maintained 
thereafter.  At  the  start  raise  the  safety-tube  of  the 
Woulff  bottle  out  of  the  liquid,  and  attach  a  piece 


UNSATURATED  HYDROCARBONS 


301 


of  tubing.  By  means  of  this  tube  bubble  the 
evolved  ethylene  through  a  mixture  of  solutions  of 
potassium  permanganate  and  sodium  carbonate  in  a 
test-tube  (Von  Baeyer's  reagent l)  until  the  pink 
color  is  lost  and  a  brownish  precipitate  of  hydrated 
manganese  dioxide  appears.  Lower  the  safety- 
tube  and  then  begin  running  slowly  into  the  flask, 
through  the  dropping  funnel,  a  mixture  of  alcohol 


FIG,  24. 

and  sulphuric  acid  (100  c.c.  of  the  former  to  85  c.c. 
of  the  latter).     Keep  up  a  steady  production  of 
ethylene  until  the  bromine  is  almost  decolorized. 
The  bromine  bottles  should  stand  in  ice-water. 
Disconnect  the  flask  and  then  remove  the  flame. 

1  Von  Baeyer's  reagent  is  decolorized  by  formic  and  hydroxy- 
benzoic  acids,  by  malonic  ether,  phenols,  aldehyde,  benzalde- 
hyde,  aldehyde  bisulphite,  acetone,  acetophenone,  glycerol,  and 
some  sugars  (because  of  oxidation  of  these  substances),  as  well 
as  by  unsaturated  compounds. 


302  ORGANIC  CHEMISTRY 

Wash  the  ethylene  bromide  with  water  in  a  separat- 
ing funnel,  and  finally  shake  it  with  NaOH  solution. 
Draw  off  the  bromide  into  a  flask,  add  dry  calcium 
chloride,  and  cork.  After  a  day  or  so  distill,  noting 
the  boiling-point  (130.3°,  but  129.5°  at  730  mm.). 
Also  take  the  specific  gravity  (2.1785  at  20°).  The 
bromide  is  easily  solidified,  melting  at  9.5°. 

(2)  Bubble  coal  gas  into  Von  Baeyer's  reagent, 
as  above. 

Allyl  alcohol  (propenol),  CH2=CH  •  CH2OH,  is  an 
unsaturated  alcohol  corresponding  to  the  hydro- 
carbon propene,  CH2=CH  •  CH3.  Its  radicle,  C3H5, 
is  called  allyl.  This  alcohol  can  be  made  from  gly- 
cerol. 

Acrolein  (acrylic  aldehyde),  CH2— CH •  CHO,  is 
the  aldehyde  from  the  above  alcohol.  It  is  pro- 
duced from  glycerol  (see  p.  202) : 

OH    OH     H       H 
CH2— CH— CH— O  =  CH2=CH— CHO+2H20. 

(Glycerol)  (Acrolein) 

EXPERIMENT.  In  a  dry  test-tube  mix  4  c.c. 
glycerol  and  0.3  c.c.  of  85%  phosphoric  acid.  Fit 
the  tube  with  a  stopper  and  bent  delivery  tube. 
Dip  the  end  of  this  tube  in  2  c.c.  of  water  in  a  small 
test-tube.  Heat  the  glycerol  to  a  high  temperature. 
Finally  test  the  solution  for  reducing  power  and  with 
SchhT s  reagent  (aldehyde  tests). 

By  oxidation  it  becomes  acrylic  acid, 
= CH-COOH. 


UNSATURATED  HYDROCARBONS  303 

Crotonic  acid  is  CH3-CH     CH-COOH. 
Oleic  acid  is  a  member  of  the  acrylic  acid  series. 
It  has  the  formula, 

CH3(CH2)7CH=CH(CH2)7COOH. 

It  is  contained  in  combination  with  glycerol  as 
glyceryl  trioleate,  in  many  oils,  as  in  olive  oil  and 
whale  oil,  and  in  animal  fats.  Oleic  acid  forms 
crystals,  melting  at  14°.  Hydriodic  acid  converts 
it  into  stearic  acid;  this  is  brought  about  by  addition 
of  hydrogen,  thus  :  ;  .  " 


CisH3402  +2H  = 

(Oleic  acid)  (Stearic  acid) 

This  reaction  is  now  taken  advantage  of  commer- 
cially in  the  process  of  hydrogenation  of  oils,  by  which 
they  are  converted  into  solid  fats.  In  this  process 
hydrogen  gas  is  used,  and  a  catalyzer  (generally 
nickel)  is  employed  to  facilitate  reaction  with  the 
olein.  Fusion  with  caustic  potash  results  in  the 
formation  of  palmitic  and  acetic  acids. 

EXPERIMENTS.  (1)  Dissolve  two  drops  of  oleic 
acid  in  a  few  cubic  centimeters  of  ether  in  a  test- 
tube;  shake  with  a  little  Von  Baeyer's  reagent 
(see  p.  301). 

(2)  Shake  some  ether  with  a  little  bromine  water; 
the  ether  becomes  yellow.  Add  a  few  drops  of 
oleic  acid  and  shake.  The  bromine  is  taken  up, 
so  that  the  color  is  lost. 

Erucic   acid,  CH3(CH2)7-CH==  CH(CH2)nCOOH, 

is  present  in  some  oils,  as  cod-liver  oil. 


304  ORGANIC  CHEMISTRY 

Linoleic  acid,  CirHsi-COOH,  is  believed  now  to 
be  an  acid  somewhat  similar  to  oleic  acid,  but  it  has 
two  double  linkings  instead  of  one.  Its  molecule 
takes  up  four  Br  atoms,  producing  tetrabromstearic 
acid.  Its  glyceryl  ester  is  contained  in  linseed  oil. 
It  has  the  power  of  taking  up  oxygen  from  the  air 
and  becoming  a  hard  solid  substance,  hence  its  use 
in  paints. 

Ricinoleic  acid, 

CH3(CH2)5CH(OH).CH2.CH== CH(CH2)7COOH, 

is  present  in  castor  oil  in  combination  with  glycerol. 
ACETYLENES 

These  hydrocarbons,  CnH2n_2,  form  a  series  of 
which  few  members  are  known. 

Acetylene,  CH^CH,  is  the  only  important  mem- 
ber. Small  quantities  are  synthesized  directly  from 
carbon  and  hydrogen  when  a  stream  of  hydrogen  is 
passed  between  the  carbon  poles  of  an  electric  arc- 
light,  a  small  quantity  of  methane  being  formed  at 
the  same  time.  It  is  formed  when  a  Bunsen  burner 
"  snaps  back."  The  gas  is  made  most  easily  and 
cheaply  by  the  action  of  water  on  calcium  carbide, 

C2Ca+2H20=C2H2+Ca(OH)2. 

When  used  with  a  special  burner,  it  gives  a  brilliant 
light,  and  is  used  as  an  illuminating  gas.  It  is  a 
colorless  gas  of  unpleasant  odor.  It  is  very  soluble 
in  acetone. 


UNSATURATED  HYDROCARBONS  305 

EXPERIMENTS.  (1)  Put  10  gm.  of  calcium  car- 
bide in  a  dry  flask  or  bottle,  cork  with  a  two-holed 
cork.  By  one  hole  suspend  a  dropping  funnel 
containing  water,  and  into  the  other  hole  fit  a  bent 
delivery  tube.  Let  the  water  drop  on  the  carbide 
very  slowly.  Bubble  the  acetylene  into  Von 
Baeyer's  reagent  until  the  test  is  secured.  Then 
connect  with  a  platinum-tipped  glass  tube  such  as 
is  used  for  burning  hydrogen.  Light  the  acetylene; 
a  brilliant  flame  is  obtained. 

(2)  Test  the  acetylene  by  inverting  a  beaker 
moistened  inside  with  a  solution  of  cuprous  chloride 
in  ammonia  over  the  stream  of  gas;  a  red  precipitate 
of  copper  acetylide,  C2CU2,  is  formed. 

Repeat  the  experiment,  causing  a  Bunsen  burner 
to  strike  back,  thus  producing  acetylene. 

The  cuprous  chloride  is  easily  prepared  as  follows : 
dissolve  0.5  gm.  of  copper  sulphate  in  a  little  water, 
add  2  c.c.  of  concentrated  ammonium  hydroxide, 
then  1.5  gm.  hydroxylamine  hydrochloride,  and 
dilute  to  25  c,c, 


CHAPTER    XXII 
SULPHUR  DERIVATIVES 

SULPHUR  may  take  the  place  of  oxygen  in  alco- 
hols or  ethers,  forming  sulphur  alcohols  and  ethers,  as 

CH3-SH  (cf.  CH3OH), 
CH3-S-CH3  (cf.  CH3OCH3). 

Sulphur  alcohols  are  called  mercaptans  or  thioal- 
cohols.  The  ethers  are  dialkyl  sulphides.  When 
they  are  oxidized,  as  with  nitric  acid,  sulphonic  acids 
are  formed,  CH3-SH+30==CH3-S03H.  The  sul- 
phonic acid  group  is  S03H. 

Sulphonic  acids  may  be  looked  upon  as  sulphuric 
acid  in  which  an  hydroxyl  group  is  replaced  by  an 
organic  group: 

/OH  /C2H5 

SO<OH     SO<OH-  : 

(Sulphuric  acid)          (Ethylsulphonic  acid) 

/3-Hydroxyethylsulphonic  acid  (isethionic  acid), 
CH2(OH)-CH2-S03H,  enters  into  the  synthesis  of 
taurin  (see  p.  272). 

A  sulphone  is  obtained  if  the  hydroxyl  of  the 
S03H  group  be  replaced  by  an  organic  radicle. 
Three  aliphatic  sulphones  are  of  importance,  be- 
cause they  are  used  as  hypnotics. 

306 


SULPHUR  DERIVATIVES  307 

Sulphonal    (sulphonemethane,    diethylsulphonedi- 


methylmethane)  ,  /Qx»/%  ~  TT  ,  is  made  from 

3O2C2H5 


acetone  and  ethyl  mercaptan.  It  forms  colorless 
crystals,  slightly  soluble  in  cold  water,  but  more 
soluble  in  hot  water. 

Trional      (sulphonethylmethane)     is     diethylsul- 
phonemethylethylmethane, 


2s\  /225 

CH3/C\S02C2H5' 
Tetronal  is  diethylsulphonediethylmethane, 

C2Hs\       /SO2C2H5 
C2H5/    \S02C2H5' 

Ichthyol  consists  for  the  most  part  of  a  mixture 
of  the  ammonium  salts  of  certain  sulphonic  acids 
derived  from  a  peculiar  tar,  obtained  by  distillation 
of  a  bituminous  shale  (found  in  the  Tyrol)  contain- 
ing the  fossil  remains  of  fishes.  It  is  said  to  contain 
about  IQ%  of  sulphur. 

There  are  several  unsaturated  compounds  con- 
taining sulphur  that  are  of  interest.  These  are  allyl 
derivatives. 

Allyl  sulphide,  (CsHs^S,  is  contained  in  oil  of  garlic. 
It  has  a  disagreeable  odor. 

^N—  C3H5 
Allyl   isothiocyanate,   C^  ,  is   a   mustard 


308  ORGANIC  CHEMISTRY 

oil.     It  is  contained  in  glucosidal  combination  in 
black  mustard  and  horse-radish. 

Allyl    thiourea    (allyl    sulphocarbamide,   thiosina- 

NH2 

is  used   as  a 


remedy. 


CHAPTER  XXIII 

CYCLIC  AND  BICYCLIC  COMPOUNDS 

THESE  form  a  transitional  group  between  the 
fatty  and  the  aromatic  compounds.1  They  con- 
tain one  or  two  closed  carbon  chains,  differing  from 
typical  aromatic  compounds  in  that  their  C  atoms 
either  have  their  full  valence  obviously  satisfied 
(saturated)  or  have  a  double  linking  which  causes 
the  compound  to  respond  to  the  tests  for  unsatura- 
tion  (cf.  benzene,  p.  321). 

CYCLIC  COMPOUNDS 

Certain  hydrocarbons  with  the  general  formula 
CnH2n  have  properties  quite  different  from  those 
of  the  ethylene  series;  indeed,  they  behave  quite 
like  members  of  the  methane  series.  Thus,  they 
do  not  reduce  Von  Baeyer's  reagent.  Therefore, 
instead  of  representing  them  as  composed  of  an 
open  chain  with  double  linkings,  their  formula  are 
written  as  closed  chains  (and  hence  they  are  called 
cyclic  compounds);  for  example,  cyclopropane, 


2x  CH2 

yCH2;   cyclopentane,     |  /CH2,    etc. 

CH/  CH2—  CH/ 

1  Cyclic  and  aromatic  compounds  have  been  classed  together 
as  homocyclic. 

309 


310  ORGANIC  CHEMISTRY 

They  are  given  the  same  names  as  the  members  of 
the  methane  series,  with  the  prefix  cyclo.  They  are 
also  called  polymethylenes,  and  the  individual 
compounds  are  trimethylene,  pentamethylene,  etc. 
Certain  of  these  cyclic  compounds  have  been  found 
in  petroleum. 

Cycloses.  There  are  a  number  of  hydroxy 
derivatives  of  the  cyclic  hydrocarbons;  these  are 
cyclic  alcohols  or  cycloses  (OH  attached  to  C  of  the 
ring).  The  most  important  of  these  is  inosite. 

Inosite,  CeH^Oe,  hexahydroxycyclohexane,  has 
the  same  empirical  formula  as  the  hexoses;  however, 
it  is  not  a  sugar.  It  occurs  in  animal  tissues  and  in 
urine,  being  from  this  source  optically  inactive; 
d  and  I  and  dl  varieties  of  inosite  are  said  to  occur 
in  plants. 

BICYCLIC   COMPOUNDS.     TERPENES   AND   CAMPHORS 

k 

In  the  volatile  oils  obtained  from  coniferous  trees 
(and  in  various  other  natural  products)  there  are 
hydrocarbons  having  the  empirical  formula  CioHie. 
These  are  called  terpenes  They  decolorize  Von 
Baeyer's  reagent  (see  p.  301),  and  they  combine 
directly  with  one  or  two  molecules  of  HC1.  They 
therefore  possess  the  general  properties  of  un- 
saturated  compounds,  but  they  differ  from  these  in 
many  respects  and  may  be  considered  to  belong  to 
the  class  of  cyclic  compounds  since  they  contain  a 
closed  chain  of  carbon  atoms.  By  mild  oxidation 
many  of  them  can  be  converted  into  cymene 
(paramethylisopropyl  benzene)  (see  p.  332),  and 
by  further  oxidation  into  paratoluic  acid  (see  p.  362) , 


CYCLIC  AND  BICYCLIC  COMPOUNDS 


311 


Thus  they  show  a  distinct  relationship  to  aromatic 
compounds,  although  they  are  not  true  aromatic 
compounds. 

The  terpenes  and  camphors  include  many  bodies 
of  medical  and  commercial  value,  and  of  these  the 
following  are  important : 

Pinene,  CioHie,  the  principal  constituent  of  oil 
of  turpentine,  has  the  structural  formula  given 
below,  and  is  optically  active.  It  is  dextrorotatory. 
Its  boiling-point  is  155°. 
When  combined  with  hydro- 
chloric acid  it  forms  pinene 
hydrochloride,  CioHirCI, 
which,  since  it  resembles 
camphor,  is  known  as  arti- 
ficial camphor  (see  exp.  be- 
low). Artificial  camphor  can 
be  converted  into  true  cam- 
phor. Oil  of  turpentine  is 
obtained  by  incising  the  bark 
of  fir-trees ;  the  crude  oil  con- 
tains, in  addition  to  turpen- 
tine, which  is  separated  by 
distillation,  residues  constituting  rosin.  By  destruc- 
tive distillation  or  by  steam  distillation  of  resinous 
waste  wood  (pine  and  fir)  there  are  obtained  wood 
turpentine  and  pine  oils.  Turpentine  boils  at  160°, 
and  has  a  specific  gravity  of  0.85.  It  hastens  the 
oxidation  of  linseed  oil,  because  it  takes  up  oxygen 
readily  from  the  air.  Pinene  can  be  converted  by 
alcohol  and  nitric  acid  into  terpin.  It  is  not 
bicyclic  like  pinene,  its  formula  being 


312  ORGANIC  CHEMISTRY 

CH3 
C—  OH 


_  CH-C(OH)<CH, 

By  taking  up  a  molecule  of  water,  terpin  hydrate 
is  formed,  which  is  a  crystalline  substance  used  as  a 
medicine. 

EXPERIMENTS.  (1)  Prepare  artificial  camphor. 
Into  10  c.c.  of  freshly  distilled  turpentine  that  is 
free  of  water  (treat  with  calcium  chloride  before  dis- 
tilling) contained  in  a  flask  kept  cool  by  a  freez- 
ing mixture,  bubble  dry  HC1  gas  until  crystals  of 
pinene  hydrochloride  appear.  Make  the  HC1  by 
heating  in  a  retort  a  mixture  of  dried  NaCl  and 
C.P.  H2S04.  Collect  the  crystals  on  a  filter  and 
examine  them. 

(2)  Shake  some  turpentine  with  Von  Baeyer's 
reagent.  Is  there  evidence  of  unsaturated  linking? 

Camphor,  CioHi6O.  This  is  a  gum  obtained  by 
distilling  with  steam  the  finely  chopped  wood  of  the 
camphor  tree.  Its  chemical  structure  has  recently 
been  worked  out,  and  it  is  now  produced  by  syn- 
thetic processes  on  a  commercial  scale.  Camphor 
contains  a  ketone  group,  so  that  it  may  be  called 
a  terpene  ketone  having  the  formula  as  shown 
below.  In  solution  it  is  dextrorotatory. 


CYCLIC  AND  BICYCLIC  COMPOUNDS 


313 


CH3 


CH2- 


CO 


CH3— C— CH3 


CH< 


CH- 


-CH< 


Borneol  is  a  secondary  terpene  alcohol  correspond- 
ing to  camphor  having  CHOH  instead  of  the  CO 
group. 

Camphor  is  convertible  into  carvacrol  (isomer  of 
thymol)  by  the  loss  of  two  atoms  of  hydrogen.  By 
warming  with  phosphorus  pentoxide  it  is  converted 
into  cymene.  It  melts  at  176.4°,  and  sublimes,  the 
sublimate  forming  crystals.  Hydroxycamphor  (oxy- 
camphor)  has  a  secondary  alcohol  group  in  the  place 
of  a  CH2  group  of  camphor.  It  is  one  of  the  newer 
remedies.  Camphor  monobromide  is  CioHi5BrO. 
Camphor  can  be  oxidized  to  camphoric  acid. 


CH 


CH; 


-COOH 


CH3— C— CH3 
CH2 CH- 


Menthol  is  a  monocyclic  terpene  alcohol  contain- 
ing a  secondary  alcohol  group  CHOH.  Its  formula 
is  given  below.  Like  camphor,  it  contains  no 
unsaturated  linkings.  Menthol  is  a  white  crystalline 
substance  melting  at  42°,  and  is  the  chief  constit- 
uent of  oil  of  peppermint.  Its  solution  is  laevorota- 


314 


ORGANIC  CHEMISTRY 


tory.     It  is  useful  as  a  medicine.     It  is  excreted  in 
combination  with  glycuronic  acid  (p.  221). 


H2C 
H2C 


CH2 


I/H 

C\ 
X)H 

/CH3. 
CH— CH< 

XCH3 


Eucalyptol    (cineol)   is    a  camphor-like  liquid  ob- 
tained from  oil  of  eucalyptus.     Its  formula  is 


CH3 

A 

) 

/CH3 

C\ 
XCH3 

V^                                            v 

HsC/NcHs 

H2cl     JCH2 
PTT 

v_/n 

Sandalwood  oil  contains  two  isomeric  unsaturated 
primary  alcohols,  one  being  bicyclic  and  the  other 
tricyclic.  They  have  the  formula,  CisH^O. 

Polyterpenes  have  two  or  more  terpene  rings. 

SUBSTANCES  ALLIED   TO   TERPENES 

Caoutchouc  or  rubber  contains  a  terpene-like 
substance.  Rubber  is  the  hardened  'milky  juice  of 
certain  tropical  plants.  Synthetic  rubber,  having 


CYCLIC  AND  BICYCLIC  COMPOUNDS  315 

similar  properties  to  natural  rubber,  has  been  pre- 
pared by  causing  isoprene, 

CH2=C(CH3)CH=CH2, 

to  polymerize.  Pure  -rubber  is  believed  to  be 
(CioHi6)n.  In  solution  it  is  in  the  colloidal  condi- 
tion. Gutta-percha  is  similar  to  rubber. 

Cholesterol  (cholesterin),  C27H460,  is  an  im- 
portant constituent  of  bile.  It  is  also  present  in 
egg  yolk,  cod-liver  oil  and  lanolin.  It  belongs  to 
a  class  of  compounds  called  sterins,  which  includes 
also  isocholesterol,  koprosterol,  phytosterol,  and 
other  substances.  It  has  an  unsaturated  linking 
and  a  secondary  alcohol  group : 


CH 


2-CHOH-CH2. 


The  portion  Ci7H26  is  believed  to  be  related  to  the 
polyterpenes.  Its  crystalline  form  is  characteristic. 
•It  melts  at  145-146°.  In  ether  solution  it  is  Isevoro- 
tatory. 

Koprosterol,  C^BUe-CHOH,  is  a  similar  com- 
pound occurring  in  the  faeces. 

Phytosterol  is  of  vegetable  origin,  being  most 
abundant  in  leguminous  seeds  and  in  vegetable  oils. 
It  can  be  detected  and  distinguished  from  choles- 
terol by  the  fact  that  its  ester  with  acetic  anhydride 
has  a  higher  melting-point  (125°)  than  the  similar 
ester  from  cholesterol  (114.5°). 


CHAPTER  XXIV 

THE  AROMATIC  HYDROCARBONS 

NEARLY  all  of  the  substances  that  we  have  so 
far  studied  are  represented  in  their  formulae  as  com- 
posed of  open  chains  of  carbon  atoms.  A  few 
of  them,  such  as  the  anhydrides  of  hydroxy-acids, 
lactones,  and  the  purin  derivatives,  have  to  be  repre- 
sented as  composed  of  closed  chains.  It  is,  however, 
only  in  the  case  of  the  aromatic  bodies  and  the  cyclic 
compounds,  that  each  link  in  the  closed  chain  is 
represented  by  a  C  atom.  In  connection  with  the 
paraffin  derivatives  containing  closed  chains,  it 
will  be  remembered  that  their  closed  chain  is  readily 
opened;  e.g.,  an  anhydride  of  an  acid  can  easily 
be  converted  into  the  corresponding  acid,  etc. 

We  come  now  to  a  group  of  organic  substances — 
the  largest  group,  indeed — the  members  of  which  are 
composed  of  closed  chains  that  cannot  readily  be 
opened.  In  the  older  chemical  nomenclature  the 
bodies  belonging  to  this  group  were  called  aromatic 
bodies  on  account  of  the  presence  of  an  agreeable 
aroma,  and  by  this  name  they  are  still  known. 
They  may  all  be  looked  upon  as  derivatives  of  a 
substance  called  benzene,  CeHe,  just  as  all  the 
fatty  substances  may  be  represented  as  derivatives 
of  methane.  Many  of  the  derivatives  of  benzene 
are  indeed  quite  analogous  with  those  of  methane, 

316 


THE  AROMATIC  HYDROCARBONS  317 

undergoing  similar  reactions  and  possessing  much  the 
same  properties.  Unlike  the  fatty  series,  few  of 
them  are  useful  as  foods;  many  of  them,  however, 
have  very  pronounced  physiological  actions.  Com- 
mercially they  are  of  very  great  value. 

There  are  four  simple  reactions  in  which  the  two 
groups  —  the  aromatic  and  the  fatty  —  give  very 
different  results: 

1.  With  concentrated  nitric  acid  the  aromatic 
hydrocarbons  readily  form  nitro  compounds,  which 
on  reduction  with  nascent  hydrogen  yield  amino- 
derivatives.  Paraffins  are  unaffected  by  HNOs. 


a. 

(Benzene)  (Nitrobenzene) 


b.  C6H5N02  +6H  =  C6H5NH2  +2H20. 

(Aniline) 

2.  With  concentrated  sulphuric  acid  they  form 
sulphonic  acids  (see  p.  306)  .     Paraffins  are  unaffected 
by  H2SO4. 

C6H5|H  +HOJ  •  S03H  =  C6H5S03H  +H2O. 

(Benzene  sulphonic  acid) 

3.  Chlor-  and  brom-benzene  are  very  stable  and 
do  not  readily  react  with  KOH,  whereas  in  the 
case  of  methyl  chloride,  etc.,  hydroxyl  can  readily 
be  substituted  for  the  Cl  (see  p.  137). 

4.  When  a  benzene  substitution  product  with  one 
or  more  side  chains  of  carbon  atoms  is  oxidized,  the 
side  chain  or  chains  become  oxidized  in  such  a  way 
as  to  form  simply  carboxyl. 


318  ORGANIC  CHEMISTRY 

BENZENE 

At  the  outset  we  must  study  the  structure  of 
benzene,  since,  as  has  been  noted,  this  is  the  mother 
substance  of  the  aromatic  bodies.  We  must  fur- 
nish evidence  that  its  formula  is  correctly  represented 
as  having  a  closed  chain. 

Benzene  1  (benzol),  CeHe.  When  coal  is  heated 
in  gas  retorts  in  the  preparation  of  artificial  gas, 
there  passes  out  with  the  gas  a  vapor  which  is  con- 
densed in  specially  arranged  condensers.  The  con- 
densed vapors  constitute  coal-tar.  The  ammonia 
and  pyridine  bases  that  are  also  given  off  from  the 
retorts  are  dissolved  in  water.  The  tar  is  a  mixture 
of  hydrocarbons,  neutral  bodies,  several  phenols, 
and  a  small  quantity  of  basic  bodies,  and  also  con- 
tains particles  of  carbon  in  suspension  (hence  its 
blackness).  The  tar  products  are  separated  partly 
by  fractional  distillation  and  partly  by  chemical 
means.  The  crude  tar  is  distilled  into  four  fractions, 
as  follows : 

(1)  Light  oil  (fraction  up  to  150°). 

(2)  Carbolic  oil  (150-210°). 

(3)  Heavy  or  creosote  oil  (210-270°). 

(4)  Anthracene  oil  (above  270°). 

The  heavy  oil  sinks  in  water;  it  contains  a  large 
amount  of  naphthalene. 

In  the  United  States  coal-tar  is  more  commonly 

distilled  into  two  fractions,  the  light  oil  to  about 

200°,    and   the   heavy   oil    above   200°.    By   this 

method  part  of  the  phenols  and  naphthalene  pass 

1  Different  from  benzine  (see  p.  121). 


THE  AROMATIC  HYDROCARBONS  319 

over  into  the  light  oil.  If  distillation  is  continued 
at  a  temperature  above  270°,  anthracene  is  obtained. 

The  residue  contains  a  large  amount  of  carbon, 
it  is  called  pitch. 

The  light  oil  is  purified  by  treatment  with  dilute 
acid  and  then  with  alkali  and  by  subsequent  dis- 
tillation. It  is  in  the  light  oil  that  most  of  the 
benzene  and  its  homologues  are  contained.  The 
benzene  can  be  further  purified  by  fractional  dis- 
tillation, then  by  treatment  with  concentrated  H^SO* 
to  remove  thiophene  (C4H4S),  and  finally  by  freez- 
ing it  and  pouring  off  the  liquid  portion. 

Benzene  may  also  be  obtained:  (1)  By  dis- 
tillation of  a  salt  of  an  aromatic  acid  with  soda- 
lime,  a  reduction  which,  it  will  be  remembered,  is 
analogous  with  that  employed  for  the  preparation  of 
methane : 

C6H5COONa+NaOH  =Na2C03+C6H6. 

(2)  By  passing  acetylene  (C2H2)  through  a  red- 
hot  tube.     This  method  illustrates  how  synthesis  of 
aromatic  out  of  fatty  hydrocarbons  can  be  accom- 
plished. 

(3)  By  heating  potassium  in  a  current  of  CO.    A 
synthesis    occurs    resulting    in    the    formation    of 
Ce(OK)6,  potassium  carbonyl.     This  is  a  derivative 
of   benzene   and   can   be   converted   into   benzene 
by   distillation  with  zinc   dust  in  the   presence  of 
water. 

Benzene  is  a  colorless  liquid  of  aromatic  odor, 
boiling  at  80.3°  (corrected)  (at  80.12°  at  757.3  mm.). 
Its  melting-point  is  5.5°.  Its  specific  gravity  is 


320  ORGANIC  CHEMISTRY 

20° 
0.8736  at  -JQ-.     It  can  be  used  for  molecular  weight 

determinations  (seep.  60).  Benzene  is  inflammable 
and  immiscible  with  water.  It  is  a  good  solvent 
for  many  substances. 

It  is  soluble  in  water  only  to  the  extent  of  0.1% 
and  it  takes  up  about  0.03%  of  water. 

EXPERIMENTS.  (1)  Mix  thoroughly  25  gm.  of 
benzoic  acid  and  50  gm.  of  powdered  quicklime, 
and  put  into  a  dry  retort  (cf .  preparation  of  methane, 
p.  120).  Connect  with  a  condenser  and  heat  grad- 
ually. Treat  the  distillate  with  dry  calcium  chloride 
and  redistill  from  a  small  fractionating  flask  (an  air- 
condenser  will  do).  Note  the  boiling-point.  Put 
the  distillate  into  a  dry  test-tube  and  cool  in  a  freez- 
ing-mixture until  crystallization  occurs.  Remove 
from  the  mixture  and  warm  the  test-tube  with  the 
fingers  while  stirring  the  crystals  with  a  thermometer. 
At  what  point  does  the  temperature  remain  constant 
while  the  crystals  are  melting? 

(2)  Determine  the  specific  gravity  of  some  pure 
benzene  at  15°  with  the  Westphal  balance. 

(3)  Shake  a  few  cubic  centimeters  of  benzene  with 
Von  Baeyer's  reagent.     Does  it  act  like  an  unsat- 
urated  compound? 

Structure  of  Benzene.  From  its  empirical  formula, 
CeHe,  one  would  expect  to  find  benzene  giving  re- 
actions like  those  of  acetylene  or  other  unsaturated 


THE  AROMATIC  HYDROCARBONS  321 

hydrocarbons,1  that  is  to  say,  reactions  indicating 
the  existence  of  double  bonds  between  the  carbon 
atoms.  Such,  however,  is  not  the  case.  Benzene 
does  not  readily  combine  with  halogens,  i.e.,  form 
addition  products;  it  is  not  sensitive  toward  oxidiz- 
ing agents;  it  does  not  decolorize  a  solution  of  potas- 
sium permanganate  containing  sodium  carbonate. 
Unsaturated  compounds  readily  give  all  these  reac- 
tions. It  is  evident,  therefore,  that  the  formula 
for  benzene  cannot  be  represented  as  containing 
double  bonds  between  the  carbon  atoms.  Further, 
the  formula  must  represent  all  the  hydrogen  atoms 
as  similarly  combined  with  the  carbon  atoms,  for 
there  are  no  isomers  of  the  monosubstitution  products 
of  benzene:  there  is  only  one  monobrombenzene, 
one  monochlorbenzene,  etc.  This  important  fact 
can  be  shown  in  a  variety  of  ways.  Perhaps  the 
simplest  is  as  follows:  If  we  treat  benzene  with 
bromine,  one  of  the  six  hydrogen  atoms  is  replaced 
by  bromine.  Numbering  the  hydrogen  atoms  thus: 

123456  1 

H  H  H  H  H  H,  let  us  suppose  that  H  is  replaced. 
Our  problem  is  to  see  whether  the  monobromben- 
zene thus  formed  is  identical  with  that  formed  by 

2  3 

replacement  of  H,  H,  etc.  To  do  this  we 
must  replace  another  H  in  the  compound, 

1         23456 

C6  Br  H  H  H  H  H  ,  by  some  group  which  can  then 

1  Cf .  dipropargyl,  C6H6,  ClfeC— CH2— CH2— C=CH.  This 
has  a  distinctly  greater  heat  of  combustion  than  benzene; 
therefore  the  kind  of  linking  that  we  have  in  benzene  must 
be  quite  different  from  that  in  ordinary  unsaturated  com- 
pounds. 


322  ORGANIC  CHEMISTRY 

be  replaced  by  Br,  the  Br  originally  present  being 
meanwhile  replaced  by  H.  This  can  be  accom- 
plished by  treating  monobrombenzene  with  nitric 
acid,  the  resulting  compound  having  the  formula 

2 

Let  us  suppose  that  H  is  replaced 


56 


by    the    NO2    group,    thus:     C6BrN02H  H  H  H. 

By  the  action  of  nascent  H  the  NO2  group  becomes 
an  amino  group,  NH2  (see  p.  376),  and  the  Br  is 
replaced  by  H.  The  formula  for  our  substance  is 

then  C6H  (NH2)  HHHH  (aniline).  By  treat- 
ing a  salt  of  aniline  (p.  384)  with  nitrous  acid  the 
diazonium  salt  is  formed,  which  by  treatment  with 
hydrobromic  acid  (see  p.  385)  yields  a  monobrom- 

2 

benzene  in  which  the  Br  atom  stands  in  place  of  H, 
and  yet  this  is  found  to  be  identical  in  properties 

with  that  monobrombenzene  hi  which  Br  was  in 

i 

place  of  H.  By  similar  reactions  the  various  H 
atoms  may  be  replaced  one  by  one,  the  result- 
ing monosubstitution  product  being  always  the 
same. 

This  fact  makes  it  evident  that  we  cannot  repre- 
sent the  C  atoms  as  linked  together  in  an  open  chain, 
for  then  there  would  necessarily  be  two  or  three 
varieties  of  monosubstitution  products,  depending 
upon  the  particular  C  atom  in  the  chain  to  which 
the  substituting  group  is  linked  (cf.  alcohols,  p.  109). 
On  this  account  Kekule,  who  had  been  a  mechanical 
engineer  before  he  became  a  chemist,  conceived  the 
notion  that  the  C  atoms  must  be  represented  as 


THE  AROMATIC  HYDROCARBONS  323 

forming  a  ring,  and  that  the  formula  for  benzene 
must  be 

CH 

x^ 

HC 


HC\  /CH 

« — — • 
CH 

or,  as  it  is  more  usually  written, 

CH 
HC/VJH 


To  satisfy  the  quadrivalence  of  the  C  atom,  it  is 
necessary,  as  shown  in  the  second  formula,  to  assume 
that  certain  of  these  bonds  are  double.  We  have, 
however,  seen  that  when  double  bonds  between  car- 
bon atoms  exist,  the  resulting  body  is  unsaturated. 
To  explain  this  apparent  inconsistency,  Kekule 
supposes  that  in  benzene  there  are  really  no  double 
bonds  in  the  same  sense  as  they  exist  in  unsaturated 
hydrocarbons,  but  that  the  double  bond  is  dynamic, 
changing  about  from  place  to  place,  and  is  really 
unrepresentable  in  a  formula.1 


1  The    centric   formula 


\V 


has   been   proposed   to   indi- 


cate  pictorially  this  self-saturation  of  the  carbon  atoms  of 
the  ring  without  definite  extra  linkings.  This  formula  also 
has  the  advantage  of  emphasizing  the  distinguishing  difference 
of  all  aromatic  from  other  organic  compounds. 


324  ORGANIC  CHEMISTRY 

Collie  has  made  an  extremely  interesting  sugges- 
tion as  to  the  spatial  relations  of  the  C  atoms  in 
benzene.  His  model  represents  each  C  atom  as  at 
the  center  of  a  tetrahedron,  and  neighboring  car- 
bons are  attached  by  bands,  while  an  H  atom  is 


FIG.  25. 


attached  to  each  C  through  the  center  of  a  face  not 
at  an  angle  of  the  tetrahedron.  The  rest  of  the 
model  is  mechanical  serving  for  support  (see  Fig.  25). 
Such  an  arrangement  permits  rotation  of  two 
kinds,  (1)  the  tetrahedra  can  rotate  on  their  own 
axes  simultaneously,  and  (2)  the  three  pairs  of 


THE  AROMATIC  HYDROCARBONS 


325 


tetrahedra  can  rotate  on  the  axes  passing  through 
the  center  of  the  model.  This  possibility  of  double 
rotation  conforms  very  well  to  the  idea  that  the 
benzene  molecule  must  be  conceived  as  a  system 
in  vibration.  By  those  rotations  the  model  can  be 
made  to  correspond  successively  to  the  following 
formulae : 


H 


/ 


The  first  and  last  would  indicate  that  there  are 
two  sets  of  H  atoms.     Possibly  this  explains  why, 


326  ORGANIC  CHEMISTRY 

in  the  substitution  of  certain  groups  for  H,  there  is 
a  tendency  to  displace  alternate  H  atoms  instead 
of  successive  ones;  for  instance,  nitric  acid  forms 

/\N°2 
N02     and    02N—        —  N02. 


In  perfect  harmony  with  this  conception  of  a  ring 
is  the  fact  that  there  are  three  kinds  of  disubstitution 
products.  That  three  and  only  three  are  possible 
will  be  evident  from  the  following  formulae,  where 
x  represents  some  substituting  group: 


, 

y-\/ 

x 


lx          * 
X\X 


A  (ortho)  B  (meta) 


C  (para) 

The  substituting  groups  may  replace  neighboring  hy- 
drogens, as  in  the  formulae  marked  A;  or  be  so  ar- 
ranged that  a  carbon  of  the  ring  intervenes,  as  in  B 
or  with  two  such  atoms  intervening,  as  in  C.  Bodies 
exhibiting  the  first  arrangement  are  called  ortho, 
the  second  meta,  and  the  third  para.1  For  certain 
1  The  abbreviations  o,  m,  and  p,  are  used  for  these  terms. 


THE  AROMATIC  HYDROCARBONS  327 

of  the  simple  disubstitution  products  of  benzene  it 
has  been  definitely  established  which  is  ortho,  which 
meta,  and  which  para.  To  ascertain  to  which  of 
these  groups  an  unknown  substance  belongs  it  is 
necessary  to  transform  it  into  one  of  the  known  sim- 
pler forms,  it  being  considered  that  the  unknown 
substance  contains  the  same  arrangement  of  its 
side  chains  as  does  the  simpler  substance  which  it 
yields.  It  remains  for  us  to  see,  therefore,  how  it  is 
possible  to  tell  to  what  class  some  simple  disub- 
stitution product  of  benzene  belongs.  This  is  done 
by  a  study  of  the  number  of  isomeric  compounds 
which  can  be  produced  by  replacing  still  another 
hydrogen  atom  of  the  ring  by  a  group  different  from 
the  other  two  groups.  Suppose  y  to  represent  this 
third  group.  In  an  ortho  compound  we  might  have 
y  attached  next  to  x, 


,  or  one  carbon  atom  removed  from  it, 


that  is  to  say,  there  might  be  two 


trisubstitution  products  which  on  removal  of  y 
would  yield  the  same  disubstitution  product.  In 
a  meta  compound  y  might  occupy  three  different 
positions;  thus,  between  the  two  x's  as  in  A,  or 
beyond  but  next  to  them  as  in  B,  or  separated 


328  ORGANIC  CHEMISTRY 

from  them  by  carbon  atoms  of  the  ring  as  in  C, 
thus: 


That  is  to  say,  there  are  three  trisubstitution  prod- 
ucts which  yield  the  same  disubstitution  product. 
In  a  para  compound  y  could  occupy  only  one  posi- 
tion, i.e.,  next  to  an  x;  therefore  there  is  only  one 
trisubstitution  product  that  could  be  converted  into 
it,  thus: 


To  take  an  example :    There  are  six  diamino- 
J 
x 

/NH2 

benzoic    acids    with    the    formula    C6H^NH2    . 

XCOOH 

By  removal  of  the  carboxyl  group  three  of  these 
yield  diaminobenzenes  which  are  identical  in  prop- 
erties (melting-point  63°),  and  which  must  there- 
fore be  meta;  two  others  yield  another  variety  of 
diaminobenzene  (melting-point,  102°)  which  must 
be  ortho;  and  the  remaining  one  yields  yet  another 
diaminobenzene  (melting-point  140°)  which  must 
be  para. 

For  convenience  of  description  it  is  customary 


THE  AROMATIC  HYDROCARBONS  329 

to  number  the  carbon  atoms  in  the  benzene  ring 
thus: 


When  three  similar  groups  (e.g.,  three  hydroxyls) 
are  attached  to  the  benzene  ring,  only  three  isomers 
are  possible,  symmetrical  (positions  1,  3  and  5), 
unsymmetrical  (1,  3,  4),  and  adjacent  (1,  2,  3). 

Analogous  to  the  alkyl  radicles  of  paraffin  hydro- 
carbons is  the  phenyl  group,  CeHs.  This  is  some- 
times designated  by  the  Greek  letter  0. 

Reaction  by  addition. — When  hydrogen  is  mixed 
with  benzene  vapor  and  the  mixture  is  passed  over 
powdered  nickel,  the  H  adds  on  to  each  carbon, 
forming  CeH^.  This  does  not  act  like  an  aromatic 
compound;  it  is  cyclohexane  (p.  309). 

HOMOLOGUES  OF  BENZENE 

Toluene   (toluol),   C6H5-CH3,  boiling-point   110°, 

20° 
specific   gravity  0.8656   at  — -^-,    can   be   separated 

from  light  oil  or  can  be  prepared  synthetically 
by  treating  a  mixture  of  monobrombenzene  and 
methyl  iodide  with  sodium  (cf .  synthesis  of  paraffins, 
p.  117). 

C6H5Br +CH3I  +2Na  =  Nal  +NaBr +C6H5CH3. 

This  reaction  clearly  illustrates  its  structure  as 
methyl  benzene.  By  oxidation  the  CH3  group 


330  ORGANIC  CHEMISTRY 

becomes  carboxyl,  benzoic  acid,  CeHsCOOH,  being 
therefore  formed. 


Xylenes,  CeBUCCHs^.  Since  they  are  disub- 
stitution  products  of  benzene,  there  are  three  of 
them.  The  boiling-point  of  ortho  is  141.9°,  meta 

20° 
139.2°,  para  138°;    the  specific  gravity  at  ~  of 

ortho  is  0.8766,  meta  0.8655,  para  0.8635.  The 
xylenes  can  be  prepared  from  light  oil.  By  oxida- 

/CH3      f  o 

tion  they  give  first  toluic  acids,  CeH4^  {  m, 

XCOOH  I  p 
/COOH  \  o 
and  then  phthalic  acids,   CeEUx  \  m.     The 

XCOOH  I  p 

xylol,  which  is  extensively  used  in  histological  work 
and  as  a  fat-solvent,  is  a  mixture  of  the  xylenes. 

Isomeric    with    the    xylenes    is    ethyl    benzene, 

Cells-  C2H5,    which    on    oxidation    yields    benzoic 

acid,    CeHsCOOH,   instead    of   toluic   or  phthalic 

acid. 

Mesitylene,    C6H3(CH3)3,     boiling-point    164.5°, 

9  8° 
specific  gravity  0.8694  at  -4^-,  is  also  contained  in 

light  oil,  and  can  likewise  be  obtained  by  a  most 
interesting  and  important  synthesis,  viz.,  by  dis- 
tilling a  mixture  of  acetone  and  sulphuric  acid  (see 
exp.  below).  Three  acetone  molecules  no  doubt 
enter  into  the  synthesis,  the  sulphuric  acid  removing 
a  molecule  of  water  from  each  and  causing  them  to 
condense  into  a  ring  as  represented  in  the  following 
formula  : 


THE  AROMATIC  HYDROCARBONS 


331 


Mild  oxidation  of  mesitylene  yields  mesitylenic 


acid,  CeHs^-CHs     ,  and  if  this  be  heated  with  soda- 

\COOH 

lime  and  the  COOH  group  be  thus  removed  (see 
p.  319),  metaxylene  is  obtained,  furnishing  corrob- 
orative proof  that  metaxylene  has  the  formula 

CH3 


CH3 


EXPERIMENT.  Preparation  of  a  benzene  hydro- 
carbon (mesitylene)  from  a  fatty  compound  (acetone). 
Into  a  500-c.c.  flask  put  100  gm.  of  clean  sand, 
50  c.c.  of  acetone,  and  a  cooled  mixture  of  65  c.c.  of 
C.P.  H2SO4  and  30  c.c.  of  water.  Mix  thoroughly 
and  allow  to  stand  for  at  least  two  days.  Filter 
with  the  aid  of  suction,  using  a  hardened  filter-paper. 
Distill  the  filtrate,  heating  the  flask  in  an  oil  bath. 
Shake  the  distillate  with  dilute  alkali,  then  with 


332  ORGANIC  CHEMISTRY 

water.  Separate  the  oily  layer,  dry  it  with  cal- 
cium chloride,  and  distill.  Collect  the  fraction 
coming  over  above  150°.  Notice  the  aromatic 
odor.  Test  it  as  follows :  Place  a  few  small  crystals 
of  anhydrous  aluminum  chloride  in  a  dry  test-tube; 
heat  gradually  until  a  thin  coating  of  sublimate  is 
secured  in  the  upper  part  of  the  tube.  When  cool 
add  a  solution  of  a  few  drops  of  the  mesitylene  in 
about  2  c.c.  of  chloroform  and  cork  the  tube.  Most 
aromatic  hydrocarbons  and  some  of  their  derivatives 
give  a  color  reaction  under  the  conditions  of  this 
test,  at  least  on  standing. 

Cymene  is  paramethylisopropyl  benzene, 

CH3 

H 

CH3 

It  can  be  obtained  by  warming  camphor,  doHi60, 
with  phosphorus  pentoxide,  or  by  treating  pinene, 
CioHl6  (from  turpentine),  with  chlorine.  It  is  a 
constituent  of  certain  ethereal  oils,  as  oil  of  eucalyptus 
and  oil  of  thyme. 


CHAPTER  XXV 

AROMATIC  HALOGEN  DERIVATIVES1 

Of  Benzene.  As  already  explained,  there  is  only 
one  kind  of  monohalogen  substitution  product  of 
benzene.  Chlor-  and  brombenzene  can  be  prepared 
by  treating  benzene  with  chlorine  or  bromine. 
lodobenzene  is  prepared  with  greater  difficulty,  it 
being  necessary  to  have  an  oxidizing  agent  present 
(I2  with  HIOs)  .  By  prolonged  action  more  than  one 
hydrogen  atom  of  the  benzene  molecule  becomes 
replaced  by  the  halogen,  and  of  course  there  are 
o-,  m-,  and  p-disubstitution  products;  indeed, 
all  the  H  atoms  may  be  replaced,  hexachlor-  (or 
brom-)  benzene  being  formed,  Cede  (or  CeBre). 
If  the  reaction  takes  place  in  direct  sunlight,  addi- 
tion products,  instead  of  substitution  products, 
are  obtained,  such  as  CeHeCle  and  CeHeBre.  These 
readily  decompose  into  the  halogen  acid  and  tri- 
substitution  products  of  benzene: 


In  contrast  to  the  halogen  derivatives  of  the  paraffins, 
the  halogen  substitution  products  of  benzene  are 

1  It  will  be  advisable  for  the  student  to  look  over  the  synop- 
sis of  aromatic  compounds  (p.  423)  frequently  in  studying  the 
following  pages. 

333 


334  ORGANIC  CHEMISTRY 

very  stable  and  do  not  readily  give  up  their  halogen 
atoms  to  be  replaced  by  hydroxyl,  a  cyanide  group, 
an  amido  group,  etc.,  as  alkyl  halides  do. 

Of  Toluene.  There  are  four  bodies  with  the 
empirical  formula  C7H7C1.  One  of  these,  called 
benzyl  chloride,  has  a  very  disagreeable  odor  and 
readily  yields  up  its  Cl  atom  when  heated  with 
hydroxides,  cyanides,  etc.  It  behaves  in  this  respect 
like  a  fatty  derivative.  These  facts  suggest  that 
the  Cl  atom  is  in  the  side  chain,  thus  C6H5CH2C1. 
That  this  is  really  so  is  proved  by  the  fact  that  when 
oxidized  it  yields  benzoic  acid,  CeHsCOOH.  It  is 
formed  when  toluene  is  treated  at  boiling  tempera- 
ture or  in  direct  sunlight  with  the  halogen. 

The  three  other  bodies  are  called  chlortoluenes  and 
have  agreeable  aromatic  odors.  They  do  not  give 
up  their  Cl  atom  when  heated  with  hydroxides,  etc. 
They  behave  in  this  respect  like  chlorbenzene,  so 
that  the  Cl  atom  must  be  present  in  direct  connec- 
tion with  the  benzene  nucleus  itself,  thus: 

/CHs 


The  three  varieties  are  ortho,  meta,  and  para. 
When  they  are  oxidized  the  Cl  atom  is  not  removed, 
but  the  CHs  side  chain  becomes  converted  into 
COOH,  a  substituted  benzoic  acid  being  thus 
formed,  i.e.,  a  chlorbenzoic  acid.  They  are  pre- 
pared by  treating  toluene  in  the  cold,  and  in  diffused 
light,  with  chlorine,  the  reaction  being  greatly 
accelerated  by  the  presence  of  antimony  trichloride 
or  some  other  halogen-carrier. 


AROMATIC  HALOGEN  DERIVATIVES  335 

In  the  same  way  with  the  di-  and  trihalogen  sub- 
stitution products  of  toluene,  substitution  may  occur 
in  either  the  phenyl l  or  the  methyl  groups.  The 
other  substitution  products  of  toluene  exhibit  a 
similar  isomerism. 

1  Phenyl  is  the  name  given  to  the  radicle  C6H5. 


CHAPTER  XXVI 
AROMATIC  HYDROXY  COMPOUNDS 

ONE  or  more  of  the  H  atoms  of  benzene  may  be 
displaced  by  a  hydroxyl  group — OH,  the  resulting 
body  being  called  a  phenol.  Phenols  manifest 
faintly  acid  properties,  so  that  some  of  them  are 
called  acids;  thus,  monohydroxybenzene  is  car- 
bolic acid,  and  trihydroxybenzene,  pyrogallic  acid. 
Their  acidity  indicates  that  in  solution  a  few  H* 
ions  are  liberated.  Compare  the  acid  power  of 
phenol  with  that  of  weak  organic  acids,  as  shown  in 
the  table  (appendix,  p.  451).  When  brought 
into  contact  with  alkaline  hydroxides,  salts,  called 
phenolates  or  phenoxides,  are  formed,  e.g.,  CeHsONa 
sodium  phenolate.  Such  phenolates  can  be  ob- 
tained by  dissolving  the  phenol  in  a  solution  of  the 
hydroxide  and  evaporating  to  dryness.  They  are, 
therefore,  stable  in  the  presence  of  water  and  thus 
differ  from  the  alcoholates,  which  are  decomposed 
by  water  and  can  be  formed  only  by  acting  on  al- 
cohol with  the  alkali  metals.  By  union  with  phenyl, 
therefore,  the  hydroxyl  group — OH  comes  to  possess 
quite  different  properties  from  those  that  it  has  when 
combined  with  a  paraffin  (see  p.  137). 

On  the  other  hand,  even  such  weak  acids  as  car- 
bonic (H2COs  or  CO2+H20)  are  more  strongly  acid 
than  phenol  and  can  decompose  phenolates,  liberat- 

336 


AROMATIC  HYDROXY  COMPOUNDS  337 

ing  the  phenol.  The  percentage  dissociation  for  a 
decinormal  solution  of  phenol  is  only  0.0037,  that 
of  carbonic  acid  being  0.174. 

In  other  respects  phenols  behave  like  tertiary 
alcohols  (cf.  tertiary  alcohol  group 


of  phenol),  thus:  they  form  ethers  and  ethereal  salts, 
but  do  not  yield  aldehydes,  ketones,  or  acids  on 
oxidation  (see  p.  112).  The  OH  group  can  be 
removed  by  treatment  with  PC15.  Using  the  same 
classification  as  for  alcohols,  we  may,  therefore,  sub- 
divide them  into  mon-,  di-,  and  triacid  phenols. 

M  ON  AC  ID  PHENOLS 


Phenol  (carbolic  acid),  CeHsOH.  This  important 
substance  is  extracted  from  the  carbolic  oil  frac- 
tion of  coal-tar  by  shaking  with  a  solution  of  alkali, 
the  carbolic  acid  in  the  resulting  solution  being 
then  precipitated  by  sulphuric  acid  and  redistilled 
(see  exp.  below).  It  is  purified  by  recrystalliza- 
tions.  It  may  also  be  prepared  by  fusing  potassium 
benzene  sulphonate  with  caustic  potash  : 

C6H5S03K  +KOH  =  C6H5OH  +K2S03, 

(Potassium  benzene  sulphonate) 

or  by  boiling  a  diazonium  salt  with  water  (see  p.  385)  : 
C6H5N2  ;  N03  +H20  =  C6H5OH  +HNO3  +N2. 

(Benzene  diazonium  nitrate) 


338  ORGANIC  CHEMISTRY 

EXPERIMENTS.  (1)  Extract  phenol  from  heavy 
oil  (carbolic  oil)  in  the  following  manner:  Dissolve 
2  c.c.  in  ether,  add  10  c.c.  of  5%  NaOH  and  shake 
for  five  minutes.  Draw  off  the  bottom  layer  with 
a  pipette  and  filter  through  a  wet  filter.  Acidulate 
the  filtrate  with  HC1,  cool,  and  shake  with  ether 
vigorously.  Remove  the  ether  layer  with  a  pipette, 
transferring  it  to  an  evaporating  dish.  Evaporate 
on  a  steam-bath  away  from  a  flame.  Note  the  odor 
of  the  residue  and  test  it  for  phenol  (see  tests,  3). 

(2)  Prepare  phenol  from  aniline.  Into  a  freshly 
made  (hot)  solution  of  12  c.c.  of  C.P.  H2S04  in  50  c.c. 
of  water  put  10  c.c.  of  aniline,  allowing  it  to  flow 
down  the  wall  of  the  beaker.  Mix  well  and  dilute 
with  100  c.c.  of  water.  Cool  with  running  water, 
then  add  sodium  nitrite  solution  (8.5  gm.  in  40  c.c. 
of  water)  until  a  drop  of  the  mixture  well  diluted 
gives  a  blue  color  to  starch-potassium-iodide  paper 
(soak  filter-paper  in  boiled  starch  solution  contain- 
ing potassium  iodide,  dry  it,  and  cut  up  into  strips), 
showing  the  presence  of  free  nitrous  acid.  This 
procedure  is  called  diazotizing,  because  the  nitrous 
acid  changes  the  aniline  salt  into  a  diazonium  salt. 
Transfer  to  a  half-liter  flask,  heat  to  40-50°  in  a 
water-bath  for  half  an  hour,  then  distill  with  steam 
(see  p.  16).  The  phenol  passes  over  into  the  con- 
denser with  the  steam.  Saturate  the  distillate 
with  sodium  chloride  and  shake  with  several  small 
portions  of  ether.  Dry  the  separated  ethereal 
extract  over  dehydrated  sodium  sulphate  for  several 
days  in  a  corked  flask.  Distill  off  the  ether  (away 
from  a  flame  if  possible,  a  steam-bath  being  safest) ; 


AROMATIC  HYDROXY  COMPOUNDS  339 

finally  draw  a  stream  of  air  through  the  hot  flask 
with  a  suction-pump.  Distill  the  phenol,  using  an 
air-condenser.  Collect  the  phenol  by  fractions, 
testing  the  first  fractions  as  in  (3)  below.  When 
a  drop  of  distillate,  on  cooling  with  water,  crystallizes, 
collect  samples. 

C6H5NH2  +H2S04  =C6H5NH2  •  H2S04, 

(Aniline)  (Aniline  sulphate) 

C6H5NH2  •  H2S04 +HN02  =  C6H5  -  N2  •  OSO3H + 2H20 

(Benzene  diazonium 
sulphate) 

C6H5  •  N2  •  OS03H  +H20    =  C6H5OH  +N2  +H2S04. 

(Phenol) 

(3)  Tests,  (a)  To  half  a  test-tube  of  phenol 
solution  add  bromine  water  until  a  white  precipitate 
of  tribromphenol  forms.  (6)  Test  some  solution 
with  a  drop  of  ferric  chloride  solution,  a  violet  color 
is  obtained,  (c)  To  a  few  cubic  centimeters  of  solu- 
tion add  Millon's  reagent  and  boil;  a  red  color 
develops,  (d)  To  10  c.c.  of  phenol  solution  add  a 
few  cubic  centimeters  of  ammonia,  then  small  por- 
tions of  bleaching-powder,  shaking  after  each  addi- 
tion, until  the  mixture  turns  blue. 

Phenol,  when  pure,  forms  colorless  rhombic  needles 
melting  at  42°  and  boiling  at  182.9°.  Its  specific 
gravity  is  1.039  at  58.5°.  It  becomes  reddish  on 
exposure  to  light.  It  dissolves  in  15  parts  of  water 
at  17°;  in  other  words,  by  shaking  phenol  crystals 
with  water  and  allowing  them  to  stand  at  room 
temperature,  an  approximately  6.5%  solution  is 
obtained,  and  the  crystals,  by  taking  up  water, 


340  ORGANIC  CHEMISTRY 

will  liquefy  and  form  an  oily  layer  at  the  bottom  of 
the  bottle.  It  mixes  with  glycerol,  alcohol  and  ether 
in  all  proportions.  The  easiest  way  to  prepare  a 
5%  phenol  solution  is  by  diluting  the  proper  quan- 
tity of  a  50%  solution  in  glycerol.  Phenol  is 
extensively  used  in  surgery  as  an  antiseptic.  It  is 
produced  in  the  intestine  by  the  action  of  micro- 
organisms on  the  aromatic  groups  in  protein;  the 
phenol  thus  produced  is  absorbed  in  the  blood  and 
unites  with  potassium  sulphate,  to  be  excreted  into 
the  urine  as  potassium  phenol  sulphate, 

C6H5-OS02OK. 

It  can  also  combine  with  glycuronic  acid.  Phenol 
uncombined  with  alkali  is  poisonous.  It  is  often 
taken  with  suicidal  intent.. 

The  derivatives  of  phenol  are  (1)  the  ethers  and 
ethereal  salts  and  (2)  the  substitution  products. 

The  ethers  are  of  two  classes :  (a)  the 
aromatic-fatty  ethers,  such  as  phenyl  ethyl  ether, 
Cells- O-C2H5,  and  (6)  the  true  aromatic  ethers, 
such  as  phenyl  ether,  C6H5  •  O  •  C6H5.  The  aromatic- 
fatty  ethers  may  be  obtained  by  allowing  an  alkyl 
halide  to  act  on  a  phenolate : 

C6H5o|Na+lIc2H5  =  C6H5  •  0  •  C2H5  +NaI. 

The  chief  members  of  this  class  are  anisole  (phenyl 
methyl  ether)  and  phenetole  (phenyl  ethyl  ether) 
They  are  both  liquids  having  pleasant  odors.  The 
true  aromatic  ethers  cannot  be  prepared  by  this 
reaction  since  a  halogen  cannot  easily  be  displaced 
from  phenyl.  They  may,  however,  be  obtained 


AROMATIC  HYDROXY  COMPOUNDS  341 

by  heating  phenol  with  a  dehydrating  agent  such  as 
aluminium  chloride: 

C6H50|H +HO|C6H5  =  C6H5  •  O  •  C6H5  +H2O  . 
The  ethereal  salts.    Phenyl  acetate,  C6H5  •  OOCCH3, 

is  a  type  of  these  and  is  prepared  by  the  action  of 
acetyl  chloride  on  phenol: 

C6H50:HTci|oCCH3  =  C6H5-OOCCH3+HC1. 

The  substitution  products  of  phenol.  In  these 
one  or  more  hydrogens  of  phenyl,  Cells,  are  replaced 
by  some  radicle,  but  the  hydroxyl  group  remains 
intact.  They  form  a  large  class,  but  only  a  few  of 
the  compounds  will  be  discussed  here,  the  most 
important  of  the  others  being  considered  later. 

Tribromphenol,  CeH^BrsOH,  is  precipitated  by 
treating  phenol  with  bromine  water  (see  exp.  above). 

Mononitrophenol,  C6H4(N02)OH,  may  be  ortho 
or  para  and  is  prepared  by  the  action  of  dilute  nitric 
acid  on  phenol. 

Trinitrophenol,  C6H2(NO2)30H,  or  picric  acid,  is 
prepared  by  allowing  strong  nitric  acid  to  act  on 
phenol  (see  exp.  below).  The  N02  groups  are 
symmetrically  attached  to  the  benzene  ring,  thus: 


02N 


It  forms  yellow  prismatic  crystals,  has  a  titter  taste, 
and  is  very  poisonous.     In  watery  solution  it  stains 


342  ORGANIC  CHEMISTRY 

silk  and  wool  yellow,  and  is  used  in  histology  for 
staining  elastic  fibers  and  also  zymogen  granules 
in  gland  cells.  Like  nitroglycerol,  it  is  an  explosive 
and  its  potassium  and  ammonium  salts  are  exten- 
sively employed  for  this  purpose.  The  substitution 
of  three  H  atoms  by  the  negative  N02  groups  in 
picric  acid  evidently  increases  its  acidity,  i.e.,  its 
dissociability  into  H  ions  (cations)  and  anions  of  the 
rest  of  the  molecule  (see  exp.  below). 

Picric  acid  has  an  anaesthetic  action  on  burns. 

By  the  action  of  phenolsulphonic  acid  on  nitrates 
production  of  picric  acid  results.  This  is  the  basis  of 
one  of  the  methods  of  estimating  small  quantities  of 
nitrates,  as  in  water  for  drinking  purposes. 

C6H4(OH)S03H+3HNO3=C6H2(OH)(NO2)3 

+H2SO4+2H2O. 

EXPERIMENTS.  (1)  Prepare  picric  acid.  Put  10 
gm.  of  C.P.  HNOs  into  a  flask,  and  add  slowly 
10  gm.  of  phenol.  When  the  action  has  subsided, 
add  30  gm.  of  fuming  nitric  acid  and  boil  until  the 
liquid  becomes  yellow.  Avoid  boiling  down  to 
dryness,  since  an  explosion  will  result.  Cool, 
dilute  the  crystalline  mass  with  water,  and  filter 
with  suction.  Wash  the  crystals  with  water,  and 
recrystallize  from  a  considerable  quantity  of  hot 
water  acidulated  with  5  drops  of  H2S(>4: 

C6H5OH+3HON02  =C6H2(N02)3(OH)  +3H20. 

(2)  Warm  gently  a  little  picric  acid  with  5  c.c.  of 
petroleum  ether  in  a  test-tube;  a  colorless  solution  is 


AROMATIC  HYDROXY  COMPOUNDS  343 

secured  (no  ionization).  Pour  the  petroleum  ether 
into  water  and  shake ;  the  water  becomes  yellow  from 
the  picric  acid  dissolved  in  it  (ionization). 

(3)  Immerse  pieces  of  woolen,  silk,  and  cotton 
cloth  in  picric  acid  solution  for  fifteen  minutes. 
Wash  them  thoroughly  with  running  water.  Which 
are  dyed? 

Aminophenols  (seep.  382). 
Phenolsulphonic  acids  (see  p.  393). 

<CHs 
.     In 
OH 

accordance  with  the  theory  it  is  possible,  by  start- 
ing from  the  corresponding  toluene-sulphonic  acids 
or  toluidines,  to  obtain  three  cresols,  viz.,  ortho, 
meta,  and  para.  The  mixture  of  cresols  is  called 
tricresol  or  cresylic  acid.  Cresol  is  also  produced 
in  the  intestine  by  the  action  of  micro-organisms  on 
protein.  Cresol  (chiefly  para)  may  be  excreted 
in  the  urine  in  combination  with  sulphuric  acid, 
exactly  as  in  the  case  of  phenol  (p.  340).  Lysol 
is  a  mixture  of  cresols  with  soap,  and  is  said  to  be 
as  strongly  germicidal  as  phenol  but  less  irritating. 
Creolin  forms  with  water  an  emulsion  of  cresols. 
These  substances  possess  antiseptic  properties  and 
are  less  poisonous  than  phenol.  They  are  extensively 
used  for  disinfecting  purposes. 

Parahydroxytolyl  mustard  oil,  obtained  by  hy- 
drolysis of  sinalbin  (p.  253),  is  a  thiocyanate  deriva- 

/OH 

tive  of  para  cresol,  CcH^^^. 

Thymol    and     carvacrol    are    isopropyl    cresols. 


344 


ORGANIC  CHEMISTRY 


That  this  is  so  is  shown  by  the  fact  that  they  can 

/CH3 
both  be  converted  into  cymene,   C6H4<C          /CH3 


CH3 

(by  removal  of  OH).  They  also  give  the  reactions 
of  phenols,  and  might  therefore  be  considered  as 
hydroxycymenes.  Thymol  is  isopropylmetacresol, 

CH3 


/CH3  (1) 
,eOH  (3) 
XC3H7  (4) 


or 


\CH; 


and  carvacrol  is  isopropylorthocresol, 

CH3 

-A 


(1) 

C6H3)H     (2) 
XC3H7  (4) 


COH 


or 


Thymol  is  contained  in  oil  of  thyme  and  is  an 
antiseptic,  being  less  poisonous  than  phenol.  The 
melting-point  of  its  crystals  is  49.4°  (corrected). 
In 'spite  of  the  fact  that  it  dissolves  only  to  the 
extent  of  about  0.1%  it  is  an  efficient  preservative 
agent.  Carvacrol  is  contained  in  oil  of  caraway. 

Aristol  (thymol  iodide)  is  dithymol  di-iodide.  It 
is  an  antiseptic  powder. 


AROMATIC  HYDROXY  COMPOUNDS  345 


DIACID  PHENOLS 

These  are  ortho,  meta,  and  para.  There  is  a 
gradation  in  melting-points,  o  104°,  ra  119°,  and  p 
169°.  (Not  all  o,  ra,  p 'compounds  show  consistent 
rise  in  melting-point  in  this  manner.)  They  all 
have  more  or  less  marked  reducing  properties,  and 
on  this  account  some  of  them  (especially  hydro- 
quinol)  are  used  as  developers  in  photography. 
With  ferric  chloride  they  all  give  color  reactions  by 
becoming  partially  oxidized. 

Orthodihydroxybenzene,  pyrocatechol  (1,  2-phen- 

OH 


H— C 

diol,     pyrocatechin,     catechol), 

H— C 


H 

can  be  made  by  fusing  orthophenol-sulphonic  acid 
with  caustic  potash.  It  is  soluble  in  water.  By 
introducing  a  methyl  radicle  in  place  of  a  hydrogen 
atom  of  one  hydroxyl  group,  guaiacol  (monomethyl 

/OCH3\ 

ether  of  pyrocatechol,   C6H4<f  )  is  obtained. 

\OH     / 

This  latter  can  also  be  separated  from  beech-wood 
tar  by  distillation  and  crystallization,  and  is  some- 
times used,  particularly  as  one  of  its  compounds, 
in  the  treatment  of  phthisis.  Guaiacol  benzoate, 
or  benzosol,  and  guaiacol  carbonate,  or  duotal, 


346 


ORGANIC  CHEMISTRY 


,  have  also  been  much  used  as 
remedies  for  tuberculosis. 
The  most  important  constituents  of  creosote  are 

/CH3 
guaiacol  and  creosols,  CeHs^- 


Metadihydroxybenzene,   resorcinol     (1,   3-phendiol, 
OH 


resorcin), 


— H 


H— 


,     is  made  by   fusing 


metabenzene-disulphonic  acid  with  caustic  potash. 
It  is  soluble  in  water,  and  its  solutions  have  a  sweet- 
ish taste.  When  heated  with  phthalic  acid  it  forms 
fluorescein  (see  exp.,  p.  372),  and  with  sodium 
nitrite  a  blue  pigment,  lacmoid,  solutions  of  which 
turn  red  with  acids. 


Paradihydroxybenzene, 


hydroquinol      (hydroqui- 
OH 


none,  quinol,  1 , 4-phendiol) , 


H— C 
H— C 


sively  used  in  photography. 


is  exten- 


AROMATIC  HYDROXY  COMPOUNDS  347 


Dihydroxytoluene,    orcinol    (orcin),    C6H3(-OH     3, 

XOH    5 

is  prepared  by  fusing  1,  3,  5-chlortoluene-sulphonic 
acid  with  caustic  potash.  On  treatment  with  am- 
monia it  absorbs  oxygen  from  the  air  and  is  converted 
into  orcein,  C28H24N207,  which  dissolves  in  alkalies 
to  form  a  dark-red  dye.  Orcein  is  used  in  histology. 
It  is  contained  in  the  natural  dye  archil,  which  is 
prepared,  like  litmus,  by  exposing  powdered  lichens 
suspended  in  ammoniacal  solution  to  the  action  of 
the  air. 

Unsaturated  derivatives  of  diacid  phenols. 

Eugenol,   or  parahydroxy-metamethoxy-allyl-ben- 


/ 
HCX 

zene,  ,  is  the  chief  sub- 

HC 


stance  in  oil  of  doves,  and  is  contained  in  other 
drugs. 

Eugenol  acetamide,  eugenol  carbinol,  eugenol 
iodide,  and  benzeugenol  have  been  put  on  the 
market  as  medicinal  preparations. 

Safrol  is  contained  in  oil  of  sassafras  and  camphor 
oil.  It  is  the  methylene  ether  of  allyl  pyrocatechol  : 

/CH2-CH—  CH2  (1) 

CcH3\o/CH2  (3  and  4)* 

Apiol  has  the  same  formula  as  safrol,  except  that 
it  has  OCHs  groups  in  the  place  of  H  in  positions 
2  and  5. 


348  ORGANIC  CHEMISTRY 


TRIACID  PHENOLS 

Pyrogallol    (pyrogallic   acid,    1,  2,  3-phentriol)   is 
•1,    2,    3    (adjacent,    see   p.    329)    trihydroxbenzene, 
C6H3(OH)3,  and  can  be  prepared  by  the  dry  distilla- 
tion of  gallic  acid  (see  exp.  below)  : 

r  roR,  /OH  (1) 

C6H2     $$«     =  CeHseOH  (2)+C02. 

X)H  (3) 

(Gallic  acid)  (Pyrogallol) 

It  forms  fine  needle-shaped  crystals  and  is  easily 
soluble  in  water.  The  solution  when  made  alkaline 
greedily  absorbs  oxygen  from  the  air,  so  that  it  is 
used  for  this  purpose  in  gas  analysis  (see  exp.  below). 
Carbonates  and  acetates  along  with  some  carbon 
monoxide  gas  are  produced  by  the  oxidation.  It  is 
also  extensively  employed  as  a  developer  in  photog- 
raphy. 

Phloroglucinol  (phoroglucin,  1,  3,  5-phentriol), 
C6H3(OH)3,  is  1,  3,  5  (symmetrical)  trihydroxy- 
benzene,  and  is  obtained  by  the  action  of  caustic 
potash  on  phloretin,  which  is  split  off  from  the  glu- 
coside  phloridzin  (see  p.  252)  by  boiling  the  latter 
with  acids. 

Phloroglucinol  is  also  employed  along  with  vanillin 
in  alcoholic  solution  as  an  indicator  (Gunzberg's 
reagent)  for  free  mineral  acid.  When  a  drop  of  this 
reagent,  mixed  with  the  acid  solution,  is  evaporated 
to  dryness,  it  gives  a  deep-red  stain  if  mineral  acid 
is  present. 

Hydroxyhydroquinol  is  asymmetrical  tri-hydroxy- 
benzene. 


AROMATIC  HYDROXY  COMPOUNDS  349 

EXPEEIMENTS.  (l)  Carefully  heat  5  gm.  of  dry 
gallic  acid  in  a  retort  or  sublimation  apparatus; 
carbon  dioxide  is  evolved  and  pyrogallol  sublimes. 
Test  some  of  the  latter  with  dilute  ferric  chloride 
solution;  an  intense  blue-black  color  is  obtained. 

(2;  Put  1  gm.  of  pyrogallol  into  a  dropping  funnel, 
add  10  c.c.  of  strong  NaOH  solution,  cork  tightly, 
and  shake  vigorously  for  a  few  minutes.  Connect 
the  stem  of  the  funnel  (after  filling  the  stem  with 
water)  with  a  burette,  the  burette  and  tubing  being 
full  of  water;  open  the  cock,  whereupon  the  water 
rises  to  take  the  place  of  the  oxygen  that  has  been 
absorbed. 

Level  up  the  water  in  the  burette  and  the  funnel, 
then  read  from  the  burette  how  much  water  was  re- 
quired to  replace  the  oxygen  that  was  absorbed. 
By  finding  how  much  more  water  is  needed  to  fill 
the  funnel  completely,  the  volume  of  unabsorbed 
air  (N2)  is  easily  determined. 

(3)  Test  solutions  of  resorcinol  and  pyrocatechol 
with  ferric  chloride;  color  reactions  are  obtained. 

AROMATIC    ALCOHOLS    (ALDEHYDES    AND   KETONES) 

Besides  the  above,  we  may  also  have  hydroxy 
derivatives  of  benzene  in  which  the  hydroxyl  group 
instead  of  replacing  one  of  the  hydrogens  of  the 
benzene  nucleus,  is  connected  with  a  side  chain. 
The  best  example  is  benzyl  alcohol,  C6H5-CH2OH, 
which  is  phenyl  carbinol.  In  their  reactions  such  al- 
cohols differ  entirely  from  phenols  and  indeed 
possess  all  the  properties  of  fatty  primary  alcohols. 
Thus,  benzyl  alcohol  can  be  prepared  by  boiling 


350  ORGANIC  CHEMISTRY 

benzyl  chloride  for  some  time  (6-8  hours)  with  water 
(cf .  synthesis  of  methyl  alcohol,  p.  137) : 

C6H5CH2|C1  +H|OH  =  C6H5  •  CH2OH  +HC1. 

(Benzyl  chloride) 

The  Cl  group,  being  in  this  case  connected  with  a 
side  chain  and  not  with  the  benzene  nucleus,  is  easily 
replaceable  by  OH.  Benzyl  alcohol  may  also  be 
made  by  treating  benzoic  aldehyde  (oil  of  bitter 
almonds)  with  nascent  hydrogen: 

C6H5  •  CHO  +2H  =  C6H5  •  CH2OH. 

(Benzoic  aldehyde) 

The  reactions  of  this  alcohol  agree  with  those  of 
fatty  alcohols:  oxidation  yields  first  an  aldehyde 
(benzaldehyde)  and  then  an  acid  (benzoic);  ethers, 
such  as  benzyl  methyl  ether  (CeHs'CEbO-CHs), 
and  ethereal  salts,  such  as  benzyl  acetate 

(C6H5CH2.OOCCH3), 

are  easily  obtained.  There  are  also  substitution 
products  (which,  however,  are  not  obtained  by  direct 
treatment)  where  one  or  more  of  the  H  atoms  of  the 
nucleus  are  replaced,  e.g.,  chlorbenzyl  alcohol, 
C6H4C1-CH2OH. 

Benzyl  alcohol,  however,  differs  in  many  respects 
from  aliphatic  alcohols;  for  instance,  it  does  not 
form  an  ester  with  sulphuric  acid.  Its  boiling-point 
is  206.5°. 

The  homologues  of  benzyl  alcohol  are  of  two  kinds : 
(a)  those  in  which  the  phenyl  group  remains  un- 
changed, but  the  alcoholic  side  chain  contains  some 
higher  fatty  radicle,  and  (b)  those  in  which  the  alco- 


AROMATIC  HYDROXY  COMPOUNDS  351 

holic  side  chain  remains  unchanged  (i.e.,  remains  as 
carbinol),  but  one  or  more  of  the  H  atoms  of  the 
benzene  nucleus  become  replaced  by  radicles,  as  in 

CH 
tolyl  carbinol, 


These  alcohols,  since  they  contain  the  primary 
alcohol'  group,  can  be  oxidized  to  aldehydes  and 
acids. 

Benzole  aldehyde  (benzaldehyde,  oil  of  bitter 
almonds),  CeHs-CHO,  is  an  important  substance, 
being  very  reactive  and  therefore  much  employed 
for  organic  synthesis.  Besides  being  produced  by 
oxidation  of  benzyl  alcohol,  it  can  be  obtained  by 
the  action  of  a  hydrolyzing  ferment  —  emulsin  —  on 
amygdalin,  a  glucoside  contained  in  bitter  almonds, 
the  stone  of  the  peach,  etc.  (see  p.  252).  The  emul- 
sin is  usually  present  along  with  the  amygdalin. 
Hydrocyanic  acid  is  also  produced  during  the  reac- 
tion: 

C20H27NOii+2H20  = 

(Amygdalin)  =  (^  .  QJJQ  +HCN  +  2C6Hi206. 

(Benzaldehyde)  (Dextrose) 

It  can  also  be  prepared  by  distilling  a  mixture  of  a 
benzoate  and  a  formate,  and  by  heating  benzal  chlo- 
ride, CeHsCHCU,  with  water  and  milk  of  lime  under 
pressure  : 

/H 
C6H5CHci+Hi  OlHl  =  C6H5-CHO+2HC1+H20. 


Commercially   it    is   made    from    benzyl    chloride. 
It  is  an  oil  of  a  pleasant  odor,  boiling  at  179°  and 


352  ORGANIC  CHEMISTRY 

having  a  specific  gravity  of  1.0504  at  15°.  Although 
relatively  insoluble  in  water,  it  is  used  as  a  flavoring 
agent.  It  is  not  poisonous.  Like  other  aldehydes, 
it  forms  addition  products  with  such  substances  as 
hydrocyanic  acid  and  acid  sulphites.  It  also  com- 
bines with  alcohols,  acids,  ketones,  etc.,  and  forms 
a  hydrazone  (see  p.  388)  with  phenylhydrazine, 
C6H5  -  CH  =  N  •  NH  -  C6H5.  When  a  solution  of  ben- 
zyl aldehyde  in  dilute  alcohol  containing  some  potas- 
sium cyanide  is  boiled,  two  molecules  of  it  condense, 
forming  benzoin,  CeHs-CHOH-COCeHs.  In  con- 
tact with  air  benzaldehyde  readily  oxidizes  to  ben- 
zoic  acid,  and  with  nascent  hydrogen  it  combines 
to  form  benzyl  alcohol. 

When  benzaldehyde  is  treated  with  acetic  anhy- 
dride, benzoyl  acetyl  peroxide, 

C6H5  •  CO— O— O— OC  •  CH3, 

is  produced.  The  formula  is  comparable  to  that  of 
hydrogen  peroxide,  H — 0 — 0 — H.  This  is  called 
acetozone  (or  benzozone)  and  is  believed  to  have 
strong  germicidal  powers  by  virtue  of  being  a  perox- 
ide. It  is  used  therapeutically  for  intestinal  dis- 
orders. 

Any  aromatic  aldehyde  when  shaken  with  strong 
KOH  and  allowed  to  stand,  undergoes  oxidation  and 
reduction  simultaneously,  the  product  being  equal 
quantities  of  alcohol  (reduction)  and  acid  (oxida- 
tion). 

EXPERIMENTS.  (1)  To  5  c.c.  of  benzyl  chloride 
in  a  small  flask  add  50  c.c.  of  water  and  5  gm. 


AROMATIC  HYDROXY  COMPOUNDS  353 

barium  nitrate,  also  some  capillary  tubes  (to  pre- 
vent bumping).  Attach  to  a  reflux  condenser  and 
boil  for  two  hours.  If  unchanged  benzyl  chlo- 
ride is  still  present,  filter.  Cool,  add  a  few  c.c. 
of  ether,  and  draw  off  the  bottom  layer  with  a 
pipette.  Shake  with  three  portions  of  ether  in  a 
separating  funnel.  Evaporate  the  ether.  Note 
the  oily  drops  and  the  odor  of  benzaldehyde.  Add 
some  Schiff's  reagent  and  warm;  a  beautiful  color 
is  developed,  which  is  intensified  on  heating,  because 
benzaldehyde  is  soluble  in  hot  water,  but  only  slightly 
soluble  in  cold  water. 

2C6H5  •  CH2C1  +Ba(N03)  2  = 

=  2C6H5  •  CHO  +BaCl2  +NO  +NO2  +H20. 

(2)  To  some  solution  of  phenylhydrazine  in  acetic 
acid  add  a  little  water  and  a  few  drops  of  benzalde- 
hyde.    Collect  the  precipitate  and  crystallize  it  from 
alcohol.     The  crystals  of  hydrazone  melt  at  152°. 

(3)  Spread  a  drop  of  benzaldehyde  on  a  watch- 
glass,  and  let  it  stand  until  crystals  of  benzoic  acid 
appear. 

(4)  Mix  10  c.c.  of  benzaldehyde  and  12  c.c.  of 
alcohol  in  a  small  flask.     Add  10  c.c.  of  10%  KCN 
solution;    now  heat,  using  a  reflux  condenser,  for 
thirty  minutes.     Cool,  filter  off  the  crystals  of  ben- 
zoin, and  recrystallize  from  hot  alcohol. 

(5)  To   a   solution   of   amygdalin   add   emulsin, 
cork  the  tube,  and  keep  at  40°  for  some  hours. 
Note  the  odor;  also  test  with  Schiff's  reagent. 

Cinnamic  aldehyde  has  the  formula 

C6H5— CH=CH— CHO. 


354  ORGANIC  CHEMISTRY 

It  is  the  essential  constituent  of  cinnamon  oil.     Syn- 
thetic cinnamic  aldehyde  is  displacing  the  natural  oil. 
Saligenin  is  both  an  alcohol  and  a  phenol;   it  is 
an  ortho  compound  having  the  formula, 

OH 


It  is  combined  with  dextrose  in  the  glucoside  salicin 
(see  p.  252). 

Ketones.  The  CO  group  may  be  attached  to  two 
phenyl  groups  (aromatic  ketones),  or  linked  to  a 
phenyl  and  fatty  group  (mixed  aromatic  fatty 
ketones). 

These  are  prepared  by  methods  analogous  with 
those  already  studied  in  connection  with  aliphatic 
ketones,  thus: 

a.  By  distilling  calcium  benzoate,  diphenyl  ketone 
or  benzophenone  is  produced: 

C6H5COlCT       !     C6H5. 

!    >Ca!=         NCG+CaCOs.   . 
C6H5|COO_  CeH/ 

(Benzophenone) 

b.  By  distilling  salts  of  two  different  aromatic 
acids,  such  as  a  salt  of  benzoic  and  one  of  toluic  acid  : 


>CO 

=  /. 

C6H5COOM          C6H5 

(Phenyltolylketone) 

1  The  salt  usually  employed  is  that  of  calcium.    M  means  a 
metal. 


AROMATIC  HYDROXY  COMPOUNDS  355 

c.  By  distilling  a  salt  of  an  aromatic  acid  with  one 
of  a  fatty  acid : 

C6H5COOM    C6H5x 

+         =         >CO+M2C03. 
CH3COOM      CH3  / 

(Methyl  phenyl  ketone  or 
acetophenone) 

Acetophenone  may  also  be  obtained  by  adding 
aluminium  chloride  to  a  mixture  of  benzene  and 
acetyl  chloride.  It  is  a  crystalline  substance  melting 
at  20.5°,  and  is  slightly  soluble  in  water.  It  is  used 
in  medicine  as  a  hypnotic  under  the  name  of 
hypnone. 


CHAPTER  XXVII 

AROMATIC  ACIDS 
MONOBASIC  ACIDS 

AROMATIC  acids  are  in  general  analogous  with  those 
of  the  paraffins,  being  monobasic,  dibasic,  etc. 
The  representative  monobasic  acid  is  benzoic, 
CeHs-COOH.  This  acid^oF\i§)  great  commercial 
value  and  of  much  physiological  interest,  since,  as 
will  be  explained  later,  it  is  the  end  product  of  the 
oxidation  in  the  animal  body  of  a  large  number  of 
benzene  derivatives  having  oxidizable  side  chains. 

It  can.  be  prepared  by  numerous  reactions,  the 
most  important  of  which  are  as  follows : 

1.  By     oxidation     of     any     benzene     derivative 
with     a     single     fatty     side     chain.      It     follows 
from   this   that    if   an    aromatic    substance    yields 
benzoic   acid   on   oxidation,   it   must   contain  only 
one    side    chain.      When    two    side    chains    exist, 
a   dibasic  acid    (phthalic)    is   obtained.     Thus  the 
hydrocarbons    of    the    benzene    series,    CeHsCHs, 
C6H5C2H5,     CeHsCaHT,    their    monacid     alcohols 
and    aldehydes,    CoHsCHsOH,    CeHsCHsCI^OH, 
CeHsCHO,  etc.,  and  their  halogen  derivatives  where 
the  halogen  is  situated  in  the  side  chain,  all  yield 
benzoic  acid  when  oxidized. 

2.  By  hydrolysis  of  benzonitrile,   CeH^CN  (see 

356 


AROMATIC  ACIDS  357 

p.  256).  The  reagent  can  be  obtained  by  substitut- 
ing the  CN  group  for  an  H  of  benzene,  either  by 
distilling  potassium  benzene  sulphonate  with  potas- 
sium cyanide, 

C6H5SO3K  +KCN  =  C6H5CN  +  K2SO3, 

or  by  heating  a  diazonium  salt  with  Cu2(CN)2  (see 
p.  385). 

3.  By  treating  benzoyl  chloride  (see  p.  359)  with 
water,  C6H5CO|C1+H|OH. 

4.  By    treating    boiling    toluene    with    chlorine, 
whereby   benzotrichloride,    CeHsCCls,    is   produced, 
which  is  then  boiled  with  water  (see  exp.  below) : 

CT~H  lOH 


Cl+H 
Cl    H 


OiH  =C6H5COOH+3HC1+H20. 
OH 


This  is  the  ordinary  commercial  method. 

5.  By  sublimation  or  treatment  of  gum  benzoin 
with  alkalies. 

6.  By  heating  hippuric  acid   (see  p.   360)   with 
hydrochloric  acid  (hydrolysis) : 


CH2COOH+H20  = 

(Hippuric  acid) 

/NH2 


Benzoic  acid  forms  needle-shaped  crystals,  which 
melt  at  121.3°  (corrected)  and  readily  sublime.  It 
is  slightly  soluble  in  cold  water,  but  its  solubility 
increases  with  rise  in  temperature  until,  at  90°, 


358  ORGANIC  CHEMISTRY 

the  water  contains  11.2%  of  the  acid,  and  the  crystals 
that  remain  undissolved  liquefy  and  form  a  layer 
beneath  the  water.  When  the  temperature  is 
further  raised  in  a  closed  tube,  the  two  layers 
gradually  mix  till,  at  116°,  a  homogeneous  liquid  is 
obtained.  Salicylic  acid  (p.  363)  behaves  in  a 
similar  manner.  The  lower  liquid  layer  is  a  solution 
of  water  in  the  acid,  not  melted  acid.  It  is  soluble 
in  alcohol  and  ether,  and  volatilizes  with  steam. 
Its  salts  and  derivatives  are  very  numerous,  and  are 
analogous  with  those  of  acetic  acid.  Most  of  them 
are  soluble  in  water. 

Of  the  metallic  salts  those  of  sodium  and  am- 
monium are  employed  as  medicines. 

The  ethereal  salts  are  prepared  in  the  same  way  as 
are  those  of  acetic  acid  (see  exp.  (1)  (a)  ). 

Balsams  (e.g.,  balsam  of  Tolu  and  balsam  of  Peru) 
contain  as  their  important  constituents  benzoic  and 
cinnamic  acids,  both  as  free  acids  and  as  their  esters 
in  combination  with  benzyl  alcohol.  Gum  benzoin 
is  a  balsam  containing  less  cinnamic  acid  than  other 
balsams. 

EXPERIMENTS.  (1)  Preparation  of  benzoic  acid. 
Put  into  a  flask  5  c.c.  of  benzotrichloride,  100  c.c. 
of  water,  and  small  pieces  of  pumice.  Attach  to  a 
reflux  condenser  and  boil  for  two  hours.  Before 
cooling  add  200  c.c.  of  hot  water  and  filter  at  once. 
Cool,  collect  the  crystals  on  a  filter,  recrystallize 
from  hot  water,  and  make  the  ethyl  benzoate  test 
on  the  dried  crystals  as  follows :  to  some  of  the  dried 
benzoic  acid  add  1  c.c.  of  alcohol  and  about  3  c.c. 


AROMATIC  ACIDS  359 

of  concentrated  H2SO4.  Heat;  just  as  it  begins 
to  boil,  notice  the  peppermint-like  odor  of  ethyl 
benzoate.  Save  a  sample  of  benzoic  acid. 

(2)  Heat  together  1  c.c.  of  benzaldehyde  and  an 
excess  of  potassium  permanganate  solution  until  the 
odor  of  benzaldehyde  is  imperceptible.     Add  per- 
manganate as  required  to  maintain  a  pink  color. 
Decolorize   with   a   few    drops   of   alcohol.     Cool, 
filter,  and  add  HC1  to  the  filtrate;    benzoic  acid 
crystallizes  out: 

C6H5CHO  +0  =  C6H5COOH. 

(3)  Sublime  benzoic   acid  from  impure  benzoic 
acid,  (see  p.  13). 

BENZOIC  ACID  DERIVATIVES 

Benzoyl  chloride,  the  acid  chloride  of  benzoic  acid, 
CeHsCOCl,  can  be  obtained  by  the  action  of  chlorine 
on  benzaldehyde,  or  by  the  action  of  PCls  on  ben- 
zoic acid:  C6H5COOH+PCl5=C6H5COCl-fPOCl3 
+HC1.  It  is  more  stable  than  acetyl  chloride,  not 
being  decomposed  by  water  in  the  cold.  It  resembles 
acetyl  chloride,  however,  in  that  it  reacts  with  the 
hydroxyl  group  of  alcohols  to  form  esters  of  ben- 
zoic acid.  The  presence  of  caustic  alkali  greatly 
facilitates  this  reaction.  It  reacts  thus  with  the 
hydroxyl  groups  in  dextrose,  the  resulting  ester  being 
insoluble  in  water  and  in  dilute  alkali. 

EXPERIMENT.  To  10  c.c.  of  10%  NaOH  add  4 
drops  of  glycerol  and  1  c.c.  of  benzoyl  chloride. 
Cork  the  tube,  and  shake  until  a  curdy  precipitate 


360  ORGANIC  CHEMISTRY 

forms,  cooling  the  tube  frequently.  Add  10  c.c. 
of  water,  shake  and  filter.  Crystallize  the  glyceryl 
tribenzoate  from  15  c.c.  of  hot  65%  alcohol. 

The  substitution  products  of  benzoic  acid  are  numer- 
ous, for  of  each  there  may  be  an  ortho,  met  a,  and 
para  variety.  They  can  be  made  by  oxidizing  the 
corresponding  substituted  toluenes,  or  by  direct 
substitution  of  one  or  more  of  the  hydrogens  of  the 
phenyl  radicle  in  benzoic  acid,  the  methods  being 
the  same  as  are  used  for  the  substitution  products  of 
benzene.  The  chlorbenzoic  acids,  the  nitrobenzoic 
acids,  the  aminobenzoic  acids,  and  the  sulpho- 
benzoic  acids  are  examples  (see  p.  394).  The 
aminobenzoic  acids  are  weaker  than  benzoic  acid, 
while  the  nitrobenzoic  acids  are  stronger. 

Novocaine  is  a  derivative  of  para-aminobenzoic 
acid,  C6H4(NH2)COO— CH2 •  CH2— N(C2H5)2 - HCL 
It  is  built  up  from  ethane  by  substitution  of  an  H 
in  each  CH3  group,  diethylamine  hydrochloride 
being  the  second  substituting  group.  It  is  a  local 
anaesthetic,  introduced  as  a  substitute  for  cocaine. 

Stovaine  and  alypin,  local  anaesthetics  of  some- 
what similar  nature,  are  also  benzoic  acid  derivatives. 

An  important  compound  of  benzoic  acid,  from  a 
biochemical  standpoint,  is  hippuric  acid.  This  is 
benzoylaminoacetic  acid,  CeHsCO-NH-CH^COOH. 
It  is  present  in  the  urine  of  herbivorous  animals, 
being  produced  in  the  kidney  by  synthesis  from 
glycin  and  benzoic  acid.  It  also  appears  in  human 
urine  when  benzoic  acid  is  administered,  or  when 


AROMATIC  ACIDS  361 

foods  yielding  it  in  the  organism  are  ingested.  It 
may  be  prepared  in  the  laboratory  by  several 
methods: 

1.  Heating  glycocoll  and  benzoic  acid  to  160°  in  a 
closed  tube. 

2.  Shaking  glycin  dissolved  in  sodium  hydroxide 
solution   with   benzoyl   chloride    (see   exp.   below): 

CeHsCOlCl +H|HNCH2COOH  = 

'  =  C6H5CO-NH-CH2COOH+HC1. 

3.  Heating  benzamide  with  chloracetic  acid  (ben- 
zamide  is  analogous  to  acetamide,  see  p.  274) : 

C6H5CONH;H  +C1 CH2COOH  = 

=  C6H5CO  -  NH  •  CH2COOH  +HC1. 

Hippuric  acid  is  relatively  insoluble  in  cold  water, 
alcohol,  and  ether,  and  forms  long  rhombic  crystals, 
having  a  melting-point  of  187.5°  (corrected).  It  is 
readily  decomposed  by  boiling  with  acids  or  alkalies, 
and  also  decomposes  when  urine  containing  it  under- 
goes fermentation. 

EXPERIMENTS.  (1)  Synthesize  hippuric  acid. 
Shake  together  4  c.c.  of  benzoyl  chloride  and  a 
solution  of  2.5  gm.  of  glycocoll  in  30  c.c.  of  10% 
NaOH  (keeping  the  flask  corked)  until  the  odor  of 
the  chloride  has  disappeared.  Cool  whenever  the 
mixture  gets  hot.  Filter,  and  acidulate  the  alkaline 
filtrate  with  HC1.  Collect  the  hippuric  acid  on  a 
filter,  wash  with  a  little  water,  press  dry  between 
filter-paper,  and  recrystallize  from  hot  water. 
Save  a  sample.  Test  part  of  it  as  follows. 


362  ORGANIC  CHEMISTRY 

(2)  (a)  Test  the  solubility  of  hippuric  acid  in 
petroleum  ether  (compare  benzoic  acid).  (6)  Heat 
a  little  dry  hippuric  acid  in  a  test-tube;  benzoic  acid 
sublimes,  while  the  residue  becomes  reddish. 

Corresponding  to  toluene  there  are  four  mono- 
basic toluic  acids.  Three  of  these  (o-,  w-,  p-)  have 

/CH3 

the  formula  CoH^  ~~  ,-,-..  and  are  made-  by  oxidiz- 
\COOH 

ing  the  corresponding  xylenes  with  nitric  acid. 
The  fourth  has  the  formula  C6H5CH2COOH,  and 
might  properly  be  called  phenyl-acetic  acid.  It  is 
obtained  by  treating  benzyl  chloride,  C6H5CH2C1, 
with  potassium  cyanide  and  hydrolyzing  the  result- 
ing nitrile  (C6H5CH2CN)  : 

C6H5CH2CN  +2H2O  =  C6H5CH2COOH  +NH3. 

A  homologue  of  this  is  phenyl-propionic  or  hydro- 
cinnamic  acid,  C6H5CH2CH2COOH. 

Cinnamic  acid  is  an  unsaturated  compound,  its 
formula  being  C6H5-CH=CH.COOH.  It  is  used 
therapeutically. 

Mandelic  acid  is  a  hydroxy  acid,  its  formula  being 
C6H5-CHOH.COOH. 

Mesitylene    yields    only    one    acid,    mesitylenic, 


.     This  is  of  importance  because  it 
COOH 

can  be  converted  into  metaxylene  by  distillation 
with  lime  (cf.  benzene,  p.  319): 


.,  =  C6H4  +CaC03. 

\COOH  XCH3  (m) 


AROMATIC  ACIDS  363 

PHENOLIC  MONOBASIC  ACIDS 

An  acid  group  may  exist  along  with  one  or  more 
phenolic  hydroxyl  groups.  According  to  the  number 
of  the  latter  groups  we  may  have  mono-,  di-,  and  tri- 
hydroxybenzoic  acids. 

/OH 

A.  Monohydroxybenzoic      acids,      C6H4\^  . 

The  ortho  variety  of  this  is  salicylic  acid,  an  extremely 
important  medicinal  substance.  Oxidation  of  the 
alcohol  saligenin  (above)  yields  salicylic  acid.  It 
may  be  prepared  by  a  variety  of  reactions,  the  chief 
of  which  are  as  follows : 

(1)  By  saponifying  methyl  salicylate  (oil  of  winter- 
green)  with  caustic  potash, 


,COO|CH 


COOK 


+CH3OH. 


OH  OH 


The  potassium  salicylate  thus  formed  can  be  decom- 
posed by  acidifying  with  hydrochloric  acid  (see  exp. 
1,  p.  366). 

(2)  By  subjecting  sodium  phenolate  to  the  ac- 
tion of  carbon  dioxide  under  pressure  (and  at  140°), 
sodium  phenyl  carbonate,  CeHsOCOONa,  is  formed, 
which  by  heating  to  140°  in  an  autoclave,  becomes 
converted  into  sodium  salicylate  (an  intramolecular 
change  taking  place)  : 

/COONa 
C6H5—  0—  COONa  =  C6H4< 

MJH 

This  method  is  used  commercially. 


364  ORGANIC  CHEMISTRY 

(3)  By  fusing  orthotoluene-sulphonic  acid,  ortho 
cresol,    or    orthosulphobenzoic    acid    with    caustic 
potash.     In  the  case  of  the  first  two  bodies  oxidation 
of  the  methyl  side  chain  occurs.     The  replacement 
of  the  sulphonic  group  by  hydroxyl  has  already  been 
explained  (cf.  p.  337). 

(4)  By  converting  orthoaminobenzoic  acid  into  the 
diazonium  salt  and  boiling  this  with  water  (see  p. 
384). 

Salicylic  acid  crystallizes  in  needles  and  melts 
at  159°  (corrected).  It  is  readily  soluble  in  hot 
water,  but  only  sparingly  so  in  cold.  Its  aqueous 
solutions  give  an  intense  violet  color  with  ferric 
chloride.  It  is  readily  soluble  in  fat-solvents. 
Solutions  of  salicylic  acid  possess  antiseptic  proper- 
ties, and,  having  no  odor,  it  is  therefore  employed 
for  preserving  wines,  foods,  etc.  Its  sodium  salt, 

/COONa 

CeH^  ,  has  great  medicinal  value  in  the 

\OH 

treatment  of  rheumatism. 

There  are  also  meta  and  para  hydroxybenzoic 
acids,  which  can  be  prepared  from  the  corresponding 
amino-  or  sulphonic-benzoic  acids.  They  do  not 
react  with  ferric  chloride. 

The  meta  and  para  acids  are  weaker  acids  than 
salicylic  acid,  and  have  a  somewhat  different  physi- 
ological action.  The  introduction  of  OH  in  the 
ortho  position  increases  the  acid  power  of  the  mole- 
cule, so  that  salicylic  acid  is  much  stronger  than  ben- 
zoic  acid. 

Salicylic  acid  forms  various  salts,  the  salicylates, 
many  of  which  are  important.  Methyl  salicylate, 


AROMATIC  ACIDS  365 

/OH 

CeH^  ,  is  the  chief  constituent  of  oil  of 

XCOOCHs 

wintergreen.  It  can  be  made  synthetically  by  heat- 
ing methyl  alcohol  with  sulphuric  acid  and  salicylic 
acid.  A  very  interesting  compound  of  salicylic  acid 

/OH 

is   phenyl   salicylate,  CeH4<r  or    salol. 

It  is  produced  by  heating  salicylic  acid  alone  to  200°- 
220°  (see  exp.  3). 

/OH  /OH 

2C6H4<  =C6H4<  +C02+H20; 

XCOOH  XCOOC6H5 

or  by  heating  phenol  and  salicylic  acid  in  the  presence 
of  phosphorus  oxy chloride: 

/OH 

3C6H4<         +3C6H5OH  +POC13  = 
XCOOH 

/OH 
=3C6H4<  +H3P04+3HC1. 


Salol  is  a  white  crystalline  powder,  somewhat  aro- 
matic in  odor  and  melting  at  43°.  It  is  insoluble 
in  water  and  unaffected  by  dilute  acids.  Alkalis 
readily  saponify  it,  however,  and  yield  salicylate 
and  phenol.  Taken  internally  it  will  therefore 
remain  undecomposed  till  it  reaches  the  intestine, 
when  the  phenol  and  salicylate  liberated  by  action 
of  the  alkali  will  act  as  antiseptics.  On  this  account 
it  has  been  used  for  intestinal  antisepsis. 


366  ORGANIC  CHEMISTRY 

EXPERIMENTS.  Salicylic  acid.  (1)  Saponify  5 
c.c.  of  oil  of  wintergreen  by  boiling  with  100  c.c.  of 
20%  NaOH,  using  a  reflux  condenser,  until  the  oil 
has  disappeared.  Cool,  acidulate  with  HC1,  collect 
the  crystals  on  a  filter,  and  wash  them  with  a 
small  quantity  of  water.  Dissolve  the  salicylic 
acid  in  a  little  hot  alcohol,  and  filter  the  solution 
into  a  beaker  half  full  of  cold  water.  Collect  the 
crystals. 

(2)  Tests,     (a)  Add   ferric   chloride   solution   to 
some  salicylic  acid  solution;    a  violet-blue  color  is 
produced.     Compare  the  similar  phenol  test.     Try 
ferric   chloride  with  alcoholic   solutions  of  phenol 
and   of   salicylic   acid,     (b)  Mix   a   little   salicylic 
acid  with  some  soda-lime  and  heat  in  a  dry  test-tube 
until  the  odor  of  phenol  is  noticed. 

(3)  Prepare  salol  as  follows:   Fill'a  dry  test-tube 
one-third  full  of  salicylic  acid,  and  fit  the  test-tube 
with  a  cork  having  a  piece  of  small  glass  tubing 
eight  inches  long  passing  through  it.     Now  heat 
gradually,   boil  the  melted  salicylic  acid  for  five 
minutes,   and,   removing   the   cork,   pour  the  hot 
liquid  into  some  cold  water  in  a  beaker.     Collect 
the  insoluble  material,  and  heat  it  with  some  water 
in  a  test-tube,  when  it  soon  melts  and  sinks  as 
dark-colored  drops.     Decant  off  the  water,  and  add 
2  c.c.  of  H^SO-i;  on  heating  a  reddish  color  de- 
velops. 

There  are  several  derivatives  of  salicylic  acid 
among  the  newer  remedies,  as  sanoform  or  di- 
iodomethyl  salicylate,  salophen  or  acetyl-para- 


AROMATIC  ACIDS  367 

minophenyl  salicylate,  and  salipyrin,  a  combination 
of  salicylic  acid  with  antipyrin. 

More  important  are  the  drugs  which  act  as  local 
anaesthetics  on  raw  surfaces,  the  orthoforms, 
anaesthesin  and  nirvanin.  * 

Orthoform  is  the  methyl  ester  of  aminohydroxy- 

/Wlz  (1) 
benzoic  acid,  C6H3^-OH  (2)  .    A  new  ortho- 

XCOOCH3  (4) 

form  has  been  prepared  in  which  the  positions  of 
OH  and  NH2  are  reversed. 

Anaesthesin  has  been  proposed  as  a  remedy  to  be 
used  in  the  place  of  orthoform;  it  is  the  ethyl  ester 
of  para-amino  benzoic  acid.  Nirvanin  is  the  methyl 
ester  of  diethylglycocoll-aminosalieylic  acid, 

/NH-OCCH2N(C2H5)2  (1) 
C6H3<-OH  (3) 

XCOOCH3  (4) 

/OOCCH3 
Aspirin  is  acetyl-salicjdic   acid,  CeH^ 

Novaspirin  is  a  citric  acid  derivative, 

/COOH 
C6H4< 

X)OCCH2v 

\      /O CH2 

/COOH         >C< 
C6H4/  /  \OC-0 

\OOCCH2X 

Both  of  the  aspirins  are  invaluable  substitutes 
for  sodium  salicylate. 


368  ORGANIC  CHEMISTRY 

Betol  is  the  0-naphthol  ester  of  salicylic  acid, 
C6H4(OH)COO.CioH7. 

B.  Dihydroxybenzoic     acid.     Protocatechuic   acid, 
/COOH  (1) 

C6H3eOH  (3)      . 
XOH  (4) 

/COOH 
Its  monomethyl  ether,  C6H3^-OCH3, 

XOH 
is  vanillic  acid,  which  is  derived  from  vanillin,  the 

/CHO 

corresponding  aldehyde,  CeHs^-OCHs,  by  oxidation. 

XOH 

Vanillin,  contained  in  the  vanilla-bean,  is  extensively 
employed  as  a  flavoring  agent.  It  is  used,  with 
phloroglucin,  as  an  indicator  for  free  mineral  acid 
(see  p.  402).  Synthetically  it  can  also  be  prepared 

/OCH3 
by  treating  guaiacol,  C«H4Vn        ?  with  chloroform 

and  caustic  soda. 

C.  Trihydroxybenzoic  acid  is  the  important  com- 

COOH  (1) 
OH  (3) 


pound   gallic   acid, 


OH  (4)  (+H20).  This 


OH  (5) 

is  contained  in  certain  plants,  but  is  most  readily 
obtained  by  boiling  tannin  with  dilute  mineral 
acid,  or  by  fermenting  oak  gallnuts.  Tannic  acid 
(tannin),  obtained  from  nutgall,  consists  of  two 
molecules  of  gallic  acid  minus  one  molecule  of  water; 
it  is  therefore  a  condensation  product. 
Tannic  acid  will  be  seen  to  bear  a  relation  to  gallic 


AROMATIC  ACIDS 


369 


acid  similar  to  that  which  disaccharides  bear  to 
monosaccharides : 

Ci4H1009  +H20  =2C7H605. 

(Tannic  acid)  (Gallic  acid) 

The  following  structural  formulae  have  been  pro- 
posed for  tannic  acid: 

H 


HO 


OH 


and 


OH 


>[COOH    HO/        N 
H  Hi  JH 


-0— OC 


Its  constitution  is  still  under  discussion. 

That  gallic  acid  has  the  structural  formula  given 
to  it  above  is  proved  by  the  fact  that  it  can  be 
prepared  by  fusing  bromprotocatechuic  acid  with 
KOH: 


COOH 

OH 

OH 

|Br       +K|OH 


=C2H2 


COOH 

OH       +KBr. 
OH 


Gallic  acid  is  almost  insoluble  in  cold  water,  but 
soluble  in  hot  water,  alcohol,  and  ether;   and  with 


370  ORGANIC  CHEMISTRY 

ferric  chloride  its  solutions  give  first  a  precipitate 
and  then  form  a  dark-green  solution.  A  blue- 
black  ink  is  made  by  adding  gallic  acid  to  a  slightly 
acid  solution  of  ferrous  sulphate  to  which  indigo 
carmine  has  also  been  added.  When  this  dries  on 
paper  it  oxidizes,  giving  a  heavy  black  precipitate. 
When  distilled,  gallic  acid  yields  pyrogallic  acid 
and  carbon  dioxide  (see  p.  349).  Airol  and  dermatol 
are  combinations  of  gallic  acid  with  bismuth. 

Tannic  acid  is  much  more  soluble  than  gallic, 
the  solution  being  colloidal.  It  gives  the  same  reac- 
tion with  ferric  chloride.  Tannic  acid  solution  is 
slightly  dextrorotatory.  It  has  a  very  extensive 
commercial  use  in  tanning,  in  which  process  it  forms 
insoluble  and  tough  compounds  with  the  protein, 
etc.,  in  skin.  It  is  also  employed,  on  account  of 
its  astringent  properties,  in  medicine.  Many  de- 
rivatives of  tannic  acid  have  been  prepared  as  sub- 
stitutes for  it,  such  as  tannalbin,  tannacol,  tannigen, 
tannoform,  etc. 

There  are  many  substances  of  vegetable  origin 
similar  in  properties  to  tannic  acid,  but  having  dif- 
ferent chemical  structure.  These  are  classed  to- 
gether as  tannins.  When  acted  upon  by  molten 
KOH  some  of  these  yield  gallic  acid,  while  others 
yield  protocatechuic  acid.  The  tannin  of  tea  and 
that  of  coffee  are  not  identical  with  tannic  acid. 

EXPERIMENTS.  (1)  Test  solutions  of  gallic  acid 
and  tannic  acid  with  ferric  chloride. 

(2)  Add  tannic  acid  solution  to  some  gelatin  solu- 
tion; the  gelatin  is  precipitated. 


AROMATIC  ACIDS  371 

(3)  To  a  solution  of  quinine  bisulphate  (quinine 
dissolved  in  very  dilute  H2SO4)  add  tannic  acid 
solution;  the  quinine  is  precipitated. 

D.  Other  phenolic   acids.    Tyrosin    is    a    phenol 
having     an     a     amino     acid     side     chain.      It 
is    parahydroxyphenyl-tf-aminoproprionic      acid, 
/OH 

C6KcH2.CHNH,COOH'  ******  *  ^^ 
from  protein.  Being  a  phenol  it  gives  a  test  with 
Millon's  reagent.  Proteins  that  contain  no  tyrosin 
(as  gelatin,  certain  albumoses,  etc.)  do  not  give  this 
test.  It  occasionally  occurs  in  the  urine  as  charac- 
teristic crystals.  Phenylalanin  is  closely  related  to 
tyrosin,  differing  only  in  not  being  a  phenol;  its 
formula  is  C6H5-CH2.CHNH2.COOH.  Homo- 
gentisic  acid  is  dihydroxyphenylacetic  acid, 

/OH  (5) 
C6H3^-OH  (2)  .     It  has  been  found  in  the 

XCH2-COOH  (1) 

urine  in  cases  of  alcaptonuria,  being  derived  from 
tyrosin  and  phenylalanin. 

DIBASIC  ACIDS 

In  agreement  with  theory,  there  are  three  of  these. 
They  are  called  phthalic  acids.  Orthophthalic  acid 
is  prepared  by  oxidizing  naphthalene  (see  p.  409) 
with  sulphuric  acid,  or  by  oxidizing  o-toluic  acid  with 
potassium  permanganate.  When  heated  it  decom- 
poses into  water  and  an  anhydride, 


372  ORGANIC  CHEMISTRY 

which  latter,  when  heated  with  phenol  in  the 
presence  of  H^SCU,  yields  phenolphthalein  (see 
exp.  3),  a  body  of  complicated  structure  used  ex- 
tensively as  an  indicator  in  volumetric  analysis, 
being  red  in  alkaline  and  colorless  in  acid  solu- 
tion (see  p.  399).  It  is  also  used  now  as  a  cathartic. 

The  meta-  and  paraphthalic  acids  do  not  form 
anhydrides.  Certain  iodine  derivatives  of  phe- 
nolphthalein, as  nosophen,  eudoxine,  and  antinosine, 
are  used  as  medicines. 

When  phthalic  anhydride  is  acted  upon  by  am- 
monia, an  acid  imide,  phthalimide, 

C=O 


is  formed.  C  =  O 

EXPERIMENTS.  (1)  Heat  some  phthalic  acid  in  a 
sublimation  apparatus  (see  'p.  13);  the  sublimate 
is  phthalic  anhydride. 

(2)  To  some  phthalic  anhydride  add  an  equal 
quantity  of  resorcinol  and  1  c.c.  of  concentrated 
H2S04,  then  warm  until  deep  red.  Dilute  with 
100  c.c.  of  water  and  render  alkaline  with  NaOH. 
The  resulting  solution  of  fluprescein  is  pinkish 
to  transmitted  light,  but  shows  a  marked  greenish 
fluorescence  to  reflected  light: 

C0\  /OH  /C0\ 

=C6H4<       >0+2H20 
\  v/  / 

HO-H,C6  C6H3-OH  ' 


0 
O' 


(Fluorescein) 


AROMATIC  ACIDS  373 

(3)  Mix  equal  quantities  of  phthalic  anhydride 
and  phenol,  add  a  little  C.P.  H2SO4,  and  warm  until 
strongly  colored.  Pour  into  a  large  quantity  of 
water.  This  solution  of  phenolphthalein  becomes 
red  when  it  is  made  faintly  alkaline  : 


(C6H4OH)2+H20. 


(Phenolphthalein) 

(4)  Prepare  eosin:  To  2.5  gms.  of  fluorescein  add 
10  c.c.  of  alcohol,  then  add,  a  drop  at  a  time,  2  c.c. 
of  bromine,  shaking  the  mixture  after  each  addition. 
When  enough  bromine  has  been  added  .to  form  di- 
bromfluorescein,  the  latter  goes  into  solution,  then  as 
tetrabromfluorescein  is  formed  it  crystallizes  out. 
After  the  mixture  has  stood  for  an  hour,  filter  and 
wash  the  crystals  with  a  little  cold  alcohol.  To  a  little 
of  the  eosin  add  NaOH  solution;  the  eosin  now  dis- 
solves, forming  a  solution  of  characteristic  red  color. 

Eosin  is  an  acid  dye,  being  the  potassium  or  sodium 
salt  of  tetrabromfluorescein, 

Br    OH 

/CO\          /       \Br 


There  is  a  hexabasic  acid,  viz.,  mellitic, 
C6(COOH)6,  which  is  present  in  the  mineral  mellite 
in  combination  with  aluminium. 


CHAPTER  XXVIII 

AROMATIC  NITROGEN  DERIVATIVES 

THERE  is  very  little  similarity  between  the  nitro- 
gen compounds  of  the  aromatic  bodies  and  those  of 
the  paraffins.  The  nitro  compounds  of  the  paraffins 
we  have  seen  to  be  of  little  importance;  those  of  the 
aromatic  bodies,  on  the  other  hand,  are  of  prime 
importance,  because  they  are  readily  produced  and 
are  easily  converted  into  other  nitrogenous  deriva- 
tives. On  this  account  nitration  forms  the  first 
step  in  many  organic  syntheses. 

NITRO  COMPOUNDS 

By  shaking  benzene  in  the  cold  with  a  mixture 
of  pure  nitric  and  sulphuric  acids,  mononitrobenzene, 
an  oily  liquid,  is  obtained.1  The  sulphuric  acid 
absorbs  the  water  produced: 

C6H6  +HN03  =  C6H5N02  +H2O 

Its  boiling-point  is  210°,  melting-point  5°,  and  its 

20° 
specific  gravity  1.2033  at  --^-. 

EXPERIMENT.  To  80  c.c.  H2S04  in  a  flask  add, 
while  shaking,  70  c.c.  of  colorless  HNO3.  Cool  thor- 

1  Mononitrobenzene  has  the  odor  of  bitter  almonds  and  is 
known  as  essence  of  mirbane.  It  is  poisonous. 

374 


AROMATIC  NITROGEN  DERIVATIVES          375 

oughly.  Add  (a  little  at  a  time)  20  c.c.  of  benzene, 
keeping  the  temperature  of  the  mixture  below  30° 
and  shaking  frequently.  Take  30  minutes  for  the 
work  of  adding  the  benzene.  Attach  a  vertical  air- 
condenser  tube;  heat  for'  an  hour  in  a  bath  kept 
at  60°,  shaking  occasionally.  Cool,  dilute  with  120 
c.c.  of  water,  pour  into  a  separating  funnel,  draw 
off  the  bottom  layer  of  acid,  and  wash  the  oil  with 
water  (the  nitrobenzene  becomes  the  bottom  layer). 
Warm  gently  with  dry  calcium  chloride  in  a  flask 
on  a  water-bath.  Distill  in  a  fractionating  flask; 
when  the  temperature  rises  above  100°  attach  an 
air-condenser,  and  observe  the  boiling-point.  Note 
the  odor  of  the  distillate. 

If,  on  the  other  hand,  the  reaction  be  allowed  to 
proceed  at  boiling  temperature  and  with  fuming 
nitric  acid  the  product  is  dinitrobenzene,  a  crystal- 
line substance  (needles)  melting  at  90°  (corrected) 
and  boiling  at  297°. 

/N02 
C6H5N02  +HN03  =  C6H4^N()  +H20. 

Although  three  varieties  of  this  are  possible,  it  is 
almost  exclusively  the  meta  form  that  is  produced. 

EXPERIMENT.  Prepare  dinitrobenzene  (meta). 
Mix  in  a  beaker  25  c.c.  of  C.P.  EUSC^  and  25  c.c. 
of  fuming  HNOs.  Immediately  add  very  slowly 
5  c.c.  of  benzene  from  a  pipette.  After  the  action 
subsides,  boil  for  a  while  and  then  pour  the  mixture 
into  250  c.c.  of  cold  water.  Filter  off  the  precipitate, 


376  ORGANIC  CHEMISTRY 

press  between  filter-paper,  and  crystallize  from  alco- 
hol. Make  a  melting-point  determination  with  dried 
crystals.  Save  a  sample  of  the  crystals. 

Toluene  and  the  xylenes  react  with  nitric  acid  in 
the  same  manner.  In  fact,  the  more  alkyl  groups 
there  are  attached  to  the  benzene  nucleus,  the  more 
easily  can  nitro  groups  be  introduced  into  it.  The 
nitro  compounds  are  very  stable. 

Trinitrotoluene  has  recently  come  into  use  as  an 
explosive. 

AMINO  COMPOUNDS 

The  most  important  reaction  of  nitro  compounds 
is  that  with  nascent  hydrogen,  whereby  they  be- 
come converted  into  amino  compounds,  of  which 
aniline  (phenylamine)  is  the  representative: 

C6H5NO2  +6H  =  C6H5NH2  +2H2O. 

(Aniline) 

Commercially,  aniline  is  produced  by  mixing 
nitrobenzene  with  iron  filings  and  hydrochloric 
acid  in  an  iron  cylinder  provided  with  a  stirring 
apparatus,  and,  when  the  action  is  over,  adding  lime 
and  distilling  the  aniline.  It  is  a  colorless  liquid 
boiling  at  183.7°  (corrected);  its  specific  gravity" 
at  16°  is  1.024.  If  not  perfectly  pure  it  becomes 
colored  on  standing.  It  is  soluble  in  about  30  parts 
of  water,  and  one  part  of  water  is  soluble  in  about 
20  parts  of  aniline  at  25°.  It  is  readily  soluble 
in  alcohol.  It  gives  several  important  color  reac- 
tions, described  in  the  experiments  below.  A 
blue  coloring  matter  is  produced  by  the  action  of 


AROMATIC  NITROGEN  DERIVATIVES.          377 

potassium  dichromate  and  sulphuric  acid  (see  2&); 
this  is  the  same  substance  as  the  first  artificial  dye- 
stuff  that  was  produced  (in  1856).  Aniline  may  be 
considered  as  NH3  in  which  one  H  is  displaced  by 
C6H5.  Like  all  such  bodies  (see  p.  258),  it  directly 
combines  with  acids  to  form  (aniline)  salts,  e.g., 
C6H5NH2.HC1;  CeHsNHs.HNOs;  C6H5NH2.H2SO4. 
The  hydrochloride  is  technically  known  as  aniline 
salt.  In  watery  solution,  however,  aniline  is  not 
alkaline  towards  litmus  and  scarcely  conducts  an 
electrical  current ;  in  other  words,  it  does  not  become 
ionized  (see  p.  65).  It  is,  therefore,  quite  different 
in  this  respect  from  aliphatic  amines,  which  with 
water  form  bases,  some  of  which  are  stronger 
even  than  ammonia  (cf-  p.  260).  Phenyl  (Cells) 
diminishes  the  basic  properties  of  the  amino  (NH2) 
group,  but  fatty  residues  increase  the  basic 
properties  of  NH2.  Whereas  nitrous  acid  decom- 
poses fatty  amines  with  liberation  of  nitrogen  (p. 
260),  it  converts  aromatic  amines  into  diazonium 
compounds  (p.  384). 

Aniline  can  be  liberated  from  the  acid  in  its  salts 
by  distilling  with  caustic  alkali : 

C6H5NH2  •  HC1 +KOH  =  C6H5NH2  +KC1 +H2O. 

It  can  also  be  obtained  by  distilling  indigo  (hence  its 
name,  anil  being  the  Spanish  for  indigo).  It  is  an 
extremely  important  substance  in  organic  synthesis. 

EXPERIMENTS.  (1)  Preparation  of  aniline.  Put 
30  gm.  of  granulated  tin  and  15  c.c.  of  nitrobenzene 
into  a  large  flask,  add  gradually  (in  portions  of 


378  ORGANIC  CHEMISTRY 

5  c.c.  each)  100  c.c.  of  C.P.  HC1,  and  cool  the  flask 
whenever  the  action  becomes  very  vigorous.  When 
all  the  acid  has  been  added,  heat  on  a  water-bath 
for  one  hour,  using  a  vertical  air-condenser.  Now 
dilute  with  50  c.c.  of  water,  cool  to  room  tempera- 
ture, pour  into  a  separating  funnel,  and  shake  with 
ether  to  remove  unchanged  nitrobenzene.  Add 
50%  NaOH  until  strongly  alkaline;  cool  the  flask 
if  the  mixture  boils.  Distill  with  steam,  until  the 
distillate  comes  clear.  Add  to  the  distillate  25  gm. 
NaCl  for  each  100  c.c.;  shake  in  a  separating  funnel 
with  three  portions  of  ether.  Dry  the  ether  extract 
with  solid  potassium  hydroxide.  Next  empty  the 
liquid  into  a  fractionating  flask,  distill  off  the  .ether, 
then  distill  the  aniline,  using  an  air-condenser. 

(2)  Tests,  (a)  Dissolve  a  little  KC103  in  0.5  c.c. 
H2SO4;  adding  a  few  drops  of  aniline  solution 
causes  a  blue- violet  color  to  appear;  diluting  with 
water  changes  it  to  red;  then  adding  ammonia 
restores  the  blue.  (6)  To  a  solution  of  aniline  in 
EbSCU  add  a  few  drops  of  potassium  dichromate 
solution;  a  blue  color  appears,  (c)  To  some  aniline 
solution  (in  water)  add  a  filtered  solution  of  bleach- 
ing-powder;  a  purple  color  develops. 

Derivatives    of    Aniline.     The   homologues   include 

/CH3 

three  toluidines,  CeEU^         ,  of  which   the  ortho 

\Nri2 

and  para  varieties  are  important,  and  six  xylidines, 

xca 


,  this  large  number  of  isomers  being 
due  to  differences  in  the  relative  positions  of  the 


AROMATIC  NITROGEN  DERIVATIVES          379 

amino  and  methyl  groups.  When  a  mixture  of  ani- 
line and  paratoluidine  is  treated  with  oxidizing 
agents,  a  compound  known  as  para-rosaniline  is 
obtained.  Many  of  the  aniline  dyes  are  derivatives 
of  this  substance.  Fucksin  is  methyl  para-rosan- 
iline, 

CH3 


H2N 


Acid  fuchsin  is  a  sulphonic  acid  derivative. 
Dyes  that  have  this  structure  are  called  the  tri- 
phenylmethane  dyes. 

EXPERIMENT.  Heat  together  in  a  test-tube  1  c.c. 
of  aniline,  1  gm.  of  paratoluidine,  and  3  gm.  HgCl2 
until  dark  red  in  color  (15  minutes  at  180-200°). 
Cool  partly,  and  extract  with  alcohol;  a  deep-red 
solution  is  obtained.  Filter,  and  evaporate  the 
filtrate. 

Replacement  of  one  or  more  of  the  H  atoms  of  the 
NEU  group  in  aniline  can  be  effected  in  various 
ways. 

By  reaction  with  alkyl  halides  secondary  and 
tertiary  mixed  aromatic  fatty  amines  are  obtained. 


380  ORGANIC  CHEMISTRY 

Thus  methyl  iodide  produces  methyl  aniline  and 
dimethyl  aniline: 

C^   TT   "\TTT;TJ    I    T Y^TT          C*    TT   "\TTT/'S<TT       TTT 

V^6-H.5-LNjiiil~rA  v^rla  =  O6-H.5iN  HU±l3  •  ±11 


Some  quaternary  base  is  also  formed  by  the  reaction. 
Dimethyl  aniline  is  commercially  the  most  im- 
portant of  these  mixed  amines  and  is  prepared  by 
heating  aniline  hydrochloride  with  methyl  alcohol, 
methyl  chloride  being  first  formed,  which  then 
reacts  as  above. 

Dimethyl  aniline  is  oxidized  to  methyl  violet,  by  the  action 
of  cupric  chloride  in  the  presence  of  potassium  chlorate,  acetic 
acid,  and  sodium  chloride;  the  copper  salt  acting  as  an  oxygen 
carrier.  Methyl  violet  2B  has  the  following  formula: 

/C6H4N(CH3)2 
C£-C6H4N(CH3)2 


\C1 

This  is  a  triphenylmethane  dye;  its  relationship  to  fuchsin 
is  indicated  by  the  chemical  name  hexamethylpararosaniline. 
Methyl  violet  B  is  pentamethylpararosaninile.  Both  of  these 
are  present  in  commercial  methyl  violet. 

Methyl  violet  is  also  called  pyoktanin.  ' 

In  a  similar  manner  replacement  with  phenyl 
groups  may  occur,  di-  and  triphenylamine  being 
produced. 

Diphenylamine,  CeHsNHCeHs,  is  obtained  by 
heating  aniline  with  aniline  hydrochloride  to  200°: 

C6H5  = 


AROMATIC  NITROGEN  DERIVATIVES  381 

Dissolved  in  concentrated  sulphuric  acid,  it  is  a 
reagent  which  detects  traces  of  nitric  acid  by 
formation  of  a  deep  blue  color.  It  is  changed  to 
tetra-phenylhydrazine. 

With  acid  chlorides,  aniline  forms  anilides,  which 
are  analogous  with  the  acid  amides  (see  p.  273)  : 

=  CH3COHNC6H5  +HC1. 

(Acetanilide) 

One  of  these,  acetanilide  (phenylacetamide)  ,  is  of 
very  great  therapeutic  interest  on  account  of  its 
antipyretic  properties.  It  is  the  active  drug  in 
many  proprietary  headache  medicines  (antikamnia, 
antifebrine,  orangine  powders,  etc.).  These  reme- 
dies are  not  entirely  harmless,  since  acetanilide  acts 
as  a  circulatory  depressant.  Acetanilide  is  easily 
prepared  by  heating  aniline  with  glacial  acetic  acid 
(see  exp.): 


=  C6H5  •  NH  •  OCCH3  +H20. 

(Acetanilide) 

EXPERIMENT.  Mix  10  c.c.  each  of  aniline  and 
glacial  acetic  acid  in  a  small  flask;  fit  with  a  long 
glass  tube  as  a  reflux  condenser  (this  allows  some  of 
the  water  of  reaction  to  escape,  but  condenses  the 
acetic  acid);  boil  for  two  hours.  Dilute  with  100 
c.c.  of  boiling  water  and  filter  at  once,  using  a  hot 
funnel.  On  cooling,  acetanilide  crystallizes  out. 
Recrystallize  from  hot  water.  Save  a  sample. 

Acetanilide  is  very  slightly  soluble  in  cold  water 
and  crystallizes  from  hot  water  in  colorless  plates. 
It  melts  at  114.2°  (corrected).  Two  other  anti- 


382  ORGANIC  CHEMISTRY 

pyretic  drugs  are  closely  related  to  acetanilide.  In 
one  of  these,  exalgin  (methyl  acetanilide),  the  hydro- 
gen atom  of  the  amido  group  is  replaced  by  methyl, 
CeHsNCHaCOCHa.  In  the  other,  benzanilide  (ben- 
zoyl  anilide),  the  acetyl  radicle  is  replaced  by  ben- 
zoyl,  CeHs-NH-OCCeHs. 

Phenol  and  amino  groups  exist  in  the  amino- 
phenols,  which  are  prepared  by  reducing  the  mono- 
nitrophenols.  The  para  variety  is  of  therapeutic 
interest.  Its  ethyl  ether  is  known  as  paraphenet- 

/OC2H5 

idm,    CeH^  _  ,  and  if  this  is   treated  with 

\NH2 

glacial  acetic  acid,  acetaminophenetole  is  formed, 

/OC2H5 

CeH4\  ,  which  is  known  in  medicine  as 

\NH-OCCH3 

phenacetin  (or  acetphenetidin)  and  is  perhaps  the 
safest  antipyretic.  Phenacetin  is  a  white  crystal- 
line substance,  sparingly  soluble  in  water,  and  with  a 
melting-point  of  135°. 

A  number  of  other  phenetidin  derivatives  are 
used  in  medicine,  particularly  holocain,  lactophenin, 
and  phenocoll.  Holocain  is 

OC2H5 
' 


NH>-C 
N/ 


Ha. 
Lactophenin  is  lactylphenetidin, 

TT 
2X15 

•OC-CHOH-CHa' 


AROMATIC  NITROGEN  DERIVATIVES          383 

Phenocoll  is  aminoacetphenetidin  (glycocoll  phen- 
etidin). 

r  H  /OCzR5 

4\NH.OC-CH2-NH2' 

Acid  and  ammo  groups.  By  reducing  the  nitro- 
benzoic  acids  with  tin  and  hydrochloric  acid  (nascent 
hydrogen)  amino  derivatives  of  benzoic  acid  may  be 
obtained  (cf.  reduction  of  nitrobenzene  to  aniline, 
p.  376).  The  ortho  variety  of  these  is  known  as 

/COOH 
anthranilic    acid,    Csl&v    -p.      .     It   is    produced 

as  an  intermediate  product  in  the  preparation  of 
aniline  by  boiling  indigo  with  caustic  alkali. 

One  of  the  most  important  nitrogenous  aromatic 
compounds  is  an  amine  derivative  of  pyrocatechol. 
Epinephrin  (adrenalin,  suprarenin)  has  the  follow- 
ing structural  formula: 


CHOH 

CH2— NH-CHs 

Epinephrin  is  the  active  principle  in  the  extract 
from  the  suprarenal  capsule,  and  when  its  solution 
is  injected  into  the  circulation  of  an  animal,  several 
important  effects  are  observed,  chief  of  which 
is  rise  of  blood-pressure.  It  is  optically  active, 


384  ORGANIC  CHEMISTRY 

(a)  D  is  -50.4  to  51.4°.  d.  I.  Suprarenin  has  been 
prepared  synthetically.  By  treating  this  with  tar- 
tar ic  acid,  crystals  can  be  obtained,  from  which 
I.  suprarenin  is  secured.  This  is  found  to  be  identical 
with  natural  epinephrin.  Synthetic  I.  suprarenin 
is  now  a  commercial  product.  It  is  advisable  to 
reserve  the  term  suprarenin  for  the  synthetically 
produced  substance.  The  physiological  action  of 
racemic  suprarenin  is  weak  compared  with  that  of 
I.  suprarenin, 

DIAZO  AND  DIAZONIUM  COMPOUNDS 

When  fatty  amino  derivatives  are  treated  with 
nitrous  acid  (see  p.  260),  nitrogen  is  evolved  and  a 
hydroxyl  group  takes  the  place  of  the  amino  group; 
with  the  aromatic  amines,  on  the  other  hand,  nitrous 
acid  at  low  temperatures  has  quite  a  different  action. 
It  converts  them  into  diazo  compounds,  so  called 
because  they  contain  two  nitrogen  (nitrogen  =  azote 
(French))  atoms  linked  together.  The  diazonium 
salts  are  of  very  great  importance  in  organic  syn- 
thesis on  account  of  the  readiness  with  which  they 
can  be  converted  into  other  bodies.  They  are 
prepared  by  treating  an  ice-cold  solution  of  an 
aniline  salt  with  nitrous  acid. 

The  diazonium  salts  are  believed  to  contain 
the  linking  —  N  —  . 


+HN02  = 

(Benzene  diazonium  nitrate) 


AROMATIC  NITROGEN  DERIVATIVES  385 

If  a  diazonium  salt  be  dried  and  struck  with  a 
hammer,  it  explodes.  Its  important  reactions  are 
as  follows: 

1.  With  water  it  forms  phenol  and  nitrogen: 

C6H5N2C1 +H2O  =  C6H5OH  +N2  +HC1. 

To  obtain  this  result  the  diazonium  salt  is  best  pre- 
pared by  treating  a  cold,  acidified  solution  of  an 
aniline  salt  with  an  equivalent  quantity  of  sodium 
nitrite,  and  then  boiling  (see  exp.  2,  p.  338). 

2.  Boiling  with  alcohol  causes  replacement  of  the 
N2  group   either   by   ethoxy  ( — O — C2Hs)    or    by 
hydrogen.     In  the  first  case  phenyl  ethyl  ether  or 
phenetole  is  formed : 

C6H5N2C1 +C2H5OH  =  C6H5OC2H5  +N2  +HC1 ; 
in  the  second  case  benzene  and  aldehyde: 
C6H5N2C1+C2H5OH=  C6H6  +CH3CHO  +N2  +HC1. 

3.  Heating  with  a  halogen  acid  or,  better  still,  with 
an  acid  solution  of  the  corresponding  cuprous  salt 
of  the  acid  causes  replacement  of  the  N2  group  by 
the  halogen: 

C6H5N2C1 +HC1  =  C6H5C1 +N2  +HC1. 

4.  Heating  with  cuprous  cyanide  replaces  the  N2 
group  by  cyanogen: 

C6H5N2Cl+Cu2(CN)2  =  C6H5CN+Cu2<^       +N2, 


386  ORGANIC  CHEMISTRY 

and  the  resulting  nitrile  can  be  hydrolyzed  to  form 
benzole  acid  (see  p.  356). 

5.  Nascent  H  changes-  a  diazonium  salt  to  phenyl- 
hydrazine  (p.  388). 

Other  replacements  by  hydrocarbon  residues, 
sulphur  groups,  etc.,  can  also  be  effected. 

EXPERIMENTS.  (1)  Prepare  benzene  diazonium 
nitrate.  Put  50  gm.  of  arsenic  trioxide  into  a 
flask;  provide  a  funnel- tube,  as  in  other  gas-gen- 
erators, and  a  delivery-tube  which  is  connected  with 
an  empty  bottle  or  cylinder  standing  in  cold  water. 
Mix  10  gm.  of  aniline  nitrate  with  12  c.c.  of  cold 
water  in  a  graduate  or  large  test-tube  standing  in 
ice-water,  and  immerse  in  the  liquid  a  delivery-tube 
coming  from  the  condenser-bottle  of  the  gas  appara- 
tus. Through  the  funnel  add  50  c.c.  of  concentrated 
HNOa  to  the  As20s;  heat  as  is  necessary  to  keep 
up  an  evolution  of  nitrogen  oxides.  Bubble  the 
gas  into  the  aniline  nitrate  mixture  until  complete 
solution  is  secured.  Add  to  the  solution  an  equal 
volume  of  alcohol  cooled  to  0°,  then  some  cold  ether. 
An  abundant  precipitate  of  benzene  diazonium  ni- 
trate is  obtained.1  Filter  quickly  with  suction. 
Test  for  the  following  reactions  at  once: 

(2)   (a)  Dissolve  some  in  water  and  let  it  stand.    It 

1 A  less  troublesome  method  of  preparation  is  as  follows : 
dissolve  5  gm.  aniline  hydrochloride  in  35  c.c.  absolute  alcohol 
which  contains  a  few  drops  of  concentrated  HC1.  Cool  to 
5°;  add  4  c.c.  ethyl  nitrite  very  slowly  while  shaking  and 
cooling.  Test  for  HN02  with  starch  iodide  paper.  Add  more 
ethyl  nitrite  if  necessary.  Let  it  stand  a  while,  then  add  cold 
ether. 


AROMATIC  NITROGEN  DERIVATIVES          387 

decomposes,  as  is  shown  by  change  of  color.  (6) 
Boil  some  with  water;  notice  the  phenol  odor, 
(c)  Boil  some  with  alcohol  in  a  test-tube;  it  is  de- 
composed with  production  of  phenetole.  (d)  Add 
some  to  a  little  concentrated  HCt  and  boil.  Chlor- 
benzene  is  formed :  on  adding  water  this  sinks  to  the 
bottom,  (e)  The  dried  salt  is  explosive;  place  a 
small  particle  on  a  piece  of  iron  and  strike  it  with  a 
hammer. 

In  all  the  above  cases  the  N2  group  is  replaced. 
Diazo  compounds,  however,  exhibit  another  type  of 
reaction  in  which  the  N2  group  is  retained  and  a  new 
substance  of  greater  stability  is  produced.  The 
more  important  of  these  substances  are : 

a.  Diazoamino  Compounds.  In  these,  one  of  the 
hydrogens  of  an  amino  group  is  replaced  by  a  diazo 
residue.  A  type  of  the  class  is  diazoaminobenzenej 
C6H5  •  N=N  •  NH  •  C6H5,  which  is  prepared  by  bring- 
ing together  aniline  and  diazonium  chloride  in  neutral 
solution.  It  forms  yellowish  crystals,  which  are  in- 
soluble in  watei  but  soluble  in  alcohol.  By  heating 
with  aniline,  and  in  various  other  ways,  diazo- 
aminobenzene  becomes  converted  by  a  rearrange- 
ment of  atoms  into 

6.  Aminoazobenzene ,  CeHs  •  N=N  •  CeH*  •  NH2, 
which  is  the  amino  derivative  of  a  substance  called 
azobenzene. 

Dimethylaminoazobenzene  is  a  derivative,  having 
the  formula, 


388  ORGANIC  CHEMISTRY 

It  is  used  as  an  indicator  for  free  acid,  giving  a  pink 
color  in  the  presence  of  the  latter  (see  p.  402). 

c.  Azobenzene,   CoHs  •  Nr=N  •  CeEU.      Azobenzene 
can  be  obtained  by  partial  reduction  of  nitroben- 
zene.    It  forms  orange-red  crystals  and  is  soluble 
in  water,  but  the  resulting  solution  is  not  a  dye  (see 
p.  407).     The  azo  group  is  present,  however,  in 
many  dyes.     It  has  been  calculated  that  the  number 
of  azo  dyes  that  can  theoretically  be  prepared  runs 
up  into  the  millions. 

d.  Hydrazobenzene,    C6H5NH—  NHC6H5,    is    ob- 
tained by  reducing  azobenzene;  it  is  colorless.     Hy- 
drazobenzene is  the  diphenyl  derivative  of  hydrazine, 
NH2—  NH2. 

Benzidine  is  produced  from  hydrazobenzene  by  the 
action  of  strong  acids,  the  latter  causing  intra- 
molecular rearrangement,  Its  formula  is 


e.  Phenylhydrazine,  CeHsNH  —  NH2,  is  the  most 
important  hydrazine  derivative.  It  forms  hydra- 
zones  (see  p.  352)  with  aldehydes,  and  osazones 
with  sugars  (see  p.  235).  It  is  obtained  by  reduc- 
tion of  diazonium  salts  (see  exp.)  : 

C6H5N2C1  +4H  =  C6H5NH—  NH2  •  HC1. 

(Phenylhydrazine  hydrochloride) 

EXPERIMENT.  To  18  c.c.  of  freshly  distilled 
aniline  add,  while  stirring,  100  c.c.  of  concentrated 
HC1.  Cool  in  a  freezing  mixture  to  0°,  add  150  gm. 
of  ice,  then  add  slowly  from  a  dropping  funnel  (have 


AROMATIC  NITROGEN  DERIVATIVES          389 

the  tip  dipping  in  the  mixture),  while  shaking,  a 
solution  of  sodium  nitrite  (14  gm.  in  70  c.c.  of  water), 
until  testing  with  starch-potassium-iodide  paper 
shows  the  presence  of  free  nitrous  acid  (blue  color). 
For  the  test  dilute  a  drop  of  the  acid  mixture  with 
5  c.c.  of  water.  During  the  diazotizing  the  tempera- 
ture must  keep  below  5°.  Add  slowly  an  ice-cold 
solution  of  60  gm.  of  stannous  chloride  in  50  c.c. 
of  concentrated  HC1.  Add  ice  to  keep  the  temper- 
ature at  0°.  Mix  thoroughly  and  let  it  stand  one 
hour.  Filter  through  muslin,  using  suction.  Trans- 
fer to  a  porous  plate,  press  out  the  phenylhydrazine 
hydrochloride  crystals  in  a  thin  layer,  and  set  away 
to  dry  out: 

1.  C6H5NH2-HC1+HN02  =  C6 


2.  C6H5N2CH-4H=C6H5NH.NH2.HC1. 

Free  phenylhydrazine  may  be  extracted  by  treat- 
ing the  hydrochloride  with  an  excess  of  NaOH 
solution  and  shaking  with  ether.  After  dehydrating 
the  ethereal  extract,  evaporate  the  ether;  phenyl- 
hydrazine remains  behind  as  a  liquid  which  readily 
solidifies  on  cooling. 

Phenylhydrazine  is  a  colorless  oil  at  ordinary 
temperature  and  boils  at  242°,  meanwhile  under- 
going some  decomposition.  It  melts  at  19°.  It  is 
poisonous.  It  becomes  dark  colored  on  exposure 
to  air.  Its  salts,  e.g.,  the  hydrochloride,  are  solid 
and  are  sometimes  employed  in  place  of  the  base 
itself  for  producing  osazone  crystals,  the  hydrochloric 
acid  being  neutralized  by  sodium  acetate. 


390  ORGANIC  CHEMISTRY 

The  relationship  of  these  bodies  to  nitrobenzene 
and  aniline  will  be  evident  from  an  examination  of 
the  following  formulae: 

C6H5-N  CeHs-NH  C6H5-NH 
C6H5N02  |  |       C6H5NH2 

(NHroben-       C6H5'N   C6H5'NH  NH2       (Aniline> 

(Azoben-  (Hydrazo-  (Phenylhydrazine) 

zene)  benzene) 


CHAPTER  XXIX 

SULPHUR  AND  ARSENIC  DERIVATIVES 
SULPHUR  DERIVATIVES 

Sulphonic  acids.  With  sulphuric  acid  the  ben- 
zenes form  sulphonic  acids,  thus: 

C6H6  +H2S04  =  C6H5S03H  +H2O 

(Benzene-sulphonic  acid) 

/CH3 

and  C6H.CHs+H2S04=C«H4<Qr._+HaO. 

^feUsxl 

(Toluene-sulphonic  acid) 

It  is  of  importance  to  note  that  in  this  respect  they 
behave  quite  differently  from  paraffins.  When  an 
alkyl  group  (as  in  toluene),  an  amino  group  (as  in 
aniline),  or  a  hydroxyl  group  (as  in  phenol)  is 
attached  to  the  benzene  nucleus,  the  sulphonic  acid 
derivative  is  more  easily  formed  than  when  benzene 
alone,  or  any  of  its  6ther  derivatives,  is  used. 

The  sulphonic  acids  are  soluble  in  water  and  are 
strong  acids,  so  that  their  salts  are  very  stable,  e.g., 
CeHsSOsNa.  Treated  with  phosphorus  pentachlor- 
ide  the  salts  of  sulphonic  acids  form  sulphonic 
chlorides,  which  may  be  reduced  to  mercaptans: 


=  C6H5S02C1  +POC13  +NaCl. 
2.  C6H5S02C1+6H=C6H5SH+HC1+2H2O. 

(Th'iopnenol) 
391 


392  ORGANIC  CHEMISTRY 

These  reactions  show  us  that  sulphonic  acids 
must  possess  an  — OH  group  and  that  the  S  atom 
is  in  immediate  connection  with  the  benzene  ring. 
The  structural  formula  of  benzene-sulphonic  acid 

O  TT 

must  therefore  be  jjQ_!\gQ     or  sulphuric    acid, 

y>S02,  in  which  one  hydroxyl  group  is  replaced 

by  phenyl  (cf.  p.  306).     They  give  several  other 
reactions,  the  following  of  which  are  important : 

1.  Fused  with  potassium  hydroxide,  benzene-sul- 
phonic acid  yields  phenol, 

C6H5S03K +KOH  =  C6H5OH  +K2S03. 

EXPERIMENTS.  (1)  To  75  gm.  of  fuming  EhSC^ 
in  a  small  flask  to  which  an  air-condenser  is  attached 
add,  a  little  at  a  time,  20  gm.  of  benzene,  shaking 
and  cooling  after  each  addition.  Transfer  to  a 
dropping  funnel,  and  run  the  mixture  out,  drop  by 
drop,  into  300  c.c.  of  cold  saturated  NaCl  solution. 
Keep  the  salt  solution  cold  with  ice-water.  On 
standing,  crystals  of  sodium  benzene  sulphonate 
form.  Crystallization  may  be  hastened  by  strongly 
cooling  some  of  the  mixture  in  a  test-tube  and 
emptying  the  crystalline  mass  into  the  main  liquid. 
Filter  the  pasty  mass  of  crystals  with  suction  and 
wash  it  with  a  little  saturated  salt  solution.  Press 
dry,  and  complete  the  drying  in  an  oven  at  110°. 

(2)  Weigh  the  dry  powder  (of  1);  weigh  out 
five  times  as  much  KOH.  Put  the  KOH  in  an 
iron  dish,  add  a  few  cubic  centimeters  of  water, 


SULPHUR  AND  ARSENIC  DERIVATIVES        393 

and  melt.  Then  add  slowly,  while  stirring  with  a 
spatula,  the  sodium  benzene  sulphonate.  Keep 
fused  for  an  hour.  Dissolve  in  water,  acidulate 
with  HC1,  shake  with  ether,  and  treat  the  ethereal 
solution  of  phenol  in  the  same  way  as  in  the  pre- 
vious phenol  experiments  (see  p.  338). 

2.  Distilled  with  potassium  cyanide,  cyanides  are 
formed  : 

C6H5S03K+KCN  =C6H5CN+K2S03 

/CH3  /CH3 

and    C6H4<+KCN=C6H4<          +K2S03. 


By  hydrolysis  these  cyanides  can  be  converted  into 
acids  : 

C6H5CN+2H20  =C6H5COOH+NH3. 

The  toluene-sulphonic  acids  may  be  ortho  or  para. 
The  meta  variety  is  rare.  The  sulphonic  acid  group 
is  present  in  many  dyestuffs  (see  p.  407). 

By   the   action    of    sulphuric    acid   on   salicylic 

/COOH  (1) 

acid,    salicyl-sulphonic    acid,   C«H4\  ,    is 

»      MjSO3H  (2) 

formed.  This  is  a  white  crystalline  deliquescent 
substance,  readily  soluble  in  water,  the  solution  being 
a  valuable  precipitant  for  certain  proteins.  Its 
solutions  on  standing  become  colored  red. 

Phenol  and  sulphonic  groups  exist  in  phenol-sul- 

/S03H 

phonic  acid,  CeH^  (o  or  p),  which  is  commer- 


cially  known  as  aseptol  and  used  as  a  disinfectant. 


394  ORGANIC  CHEMISTRY 

The  sodium  salt  of  it  is  sodium  sulphocarbolate 
(phenolsulphonate),  and  is  used  to  arrest  fermenta- 
tion in  the  stomach. 

Acid  and  sulpho  groups.  Metasulphobenzoic  acid 
is  produced  by  the  action  of  sulphuric  acid  on  ben- 
zoic  acid.  The  important  substance  saccharin  is 
the  imide  of  orthosulphobenzoic  acid, 

XX)  \ 

C6H<SO>H'      , 

and  is  also  called  benzosulphinide.  Its  sodium 
salt  (in  which  Na  replaces  H  of  NH)  is  called 
soluble  saccharin.  It  is  intensely  sweet,  and  anti- 
septic; on  account  of  these  properties  it  is  used  as 
a  medicine  and  a  preservative. 

Sulphonic  and  amino  groups.  By  the  action  of 
sulphuric  acid  on  aniline,  aniline  sulphate  is  formed, 
and  then  this  becomes  converted  by  heating  into 
paraminobenzenesulphonic  acid  or  sulphanilic  acid, 

/NH2 

<  0_      ,  by  dehydration: 
N^Os-U 

C8H5NH2  •  H2S04  =  C6H4<         '  +H2O. 


Sulphanilic  acid  is  soluble  in  hot  water,  but  only 
sparingly  so  in  cold  water.  Its  solution  is  acid  in 
reaction,  thus  differing  from  that  of  taurin  (amino- 
ethyl-sulphonic  acid,  see  p.  272).  It  is  used  in  the 
manufacture  of  dyes,  in  a  large  number  of  which 
there  exists  the  sulphonic  acid  group  along  with  a 
diazo  group.  Two  of  these  dyes,  viz.,  methyl 


SULPHUR  AND  ARSENIC  DERIVATIVES        395 

orange  and  tropaeolin  OO,  are  used  as  indicators  in 
biochemistry. 

EXPERIMENT.  Preparation  of  sulphanilic  acid.  To 
50  gm.  of  C.P.  IbSCU  in  a  flask,  add  gradually  15  c.c. 
of  aniline,  and  heat  in  an  oil-bath  at  180-190°  for 
about  four  hours,  until  a  test-drop,  diluted  with 
water  and  treated  with  NaOH,  shows  no  unchanged 
aniline.  Cool,  and  pour  into  a  beaker  of  cold  water 
while  stirring  the  latter.  Filter  off  the  crystals. 
Evaporate  the  nitrate  to  small  volume  to  secure 
more  crystals.  Recrystallize  from  hot  water. 

Helianthin  is  dimethylaminoazobenzene-sulphonic 
acid, 


,N=  N—  C6H4N(CH3)2  (1) 
C6H4\S03H  (4) 

prepared  by  acting  on  benzene-diazonium-sulphonic 
acid  with  dimethylaniline.  Its  sodium  salt  is  methyl 
orange  (see  indicators,  p.  400). 

Orange  II  is  an  azo  dye,  somewhat   related  to 
methyl  orange  in  chemical  structure: 


/N=  N  -doEe  -OH 
C6H4\S03H 

EXPERIMENT.  Dissolve  10  gm.  of  dry  sulphanilic 
acid  in  100  c.c.  of  2.5%  Na2COs  solution  (made  with 
anhydrous  carbonate),  and  add  3.5  gm.  of  NaNO2 
dissolved  in  20  c.c.  of  water.  Cool  with  ice-water, 
gradually  add  diluted  HC1  (6  c.c.  +10  c.c.  H2O), 
and  finally  add  an  acid  solution  of  dimethylaniline 


396  ORGANIC  CHEMISTRY 

(6  gm.  +6  c.c.  HC1  +20  c.c.  H2O).  Render  the  mix- 
ture alkaline  with  NaOH  solution  and  add  20  gm. 
of  NaCl.  Filter  off  the  methyl  orange  precipitate 
and  crystallize  from  hot  water.  To  a  little  dilute 
solution  of  methyl  orange  add  some  acid,  a  red 
color  is  obtained.  Save  a  sample  of  the  crystals. 
Tropseolin  OO  is  diphenyl-aminoazobenzene-sul- 

v,     •        M    n  TT  /N2-CeH4NHC6H5 
phonic  acid,  C6H4<  .     Its  solu- 


tion  gives  a  violet  color  with  free  mineral  acid; 
or,  if  its  alcoholic  solution  be  evaporated  to  dryness, 
the  resulting  residue,  gives  a  violet  color  with  free 
mineral  acids.  Applied  in  this  latter  manner 
the  test  is  very  delicate.  It  is  thus  used  as  an 
indicator  in  analysis  of  the  gastric  juice. 

Methylene  blue  (methylthionin  chloride)  is  a  dye 
containing  sulphur  in  the  chromophore  group 
(see  p.  406).  It  is  a  thiazine  derivative,  its  formula 
being: 

/\/N\. 


AROMATIC  ARSENIC  DERIVATIVES 

An  arsenic-containing  derivative  of  ortho  amino- 
phenol  has  been  recently  synthesized.  It  is  used  as 
a  remedy  for  syphilis.  Its  trade  name,  salvarsan 
(arseno-benzol  or  "  606  ")>  gives  little  idea  of  its 


SULPHUR  AND  ARSENIC  DERIVATIVES        397 

composition.     It  is  the  hydrochloride  of  dihydroxy- 
diamino-diarseno-  (di-)  benzene, 


— NH2 


Another  organic  arsenic  compound  is  atoxyl,  in  which 
an  OH  of  monosodium  arsenate  is  replaced  by  aniline, 

/NH2  (1) 
\AsO(OH)  (ONa)  (4)' 

If  the  sodium  be  substituted  by  H,  arsanilic  acid  is 
obtained.     Arsacetin  is  sodium  acetyl  arsanilate. 


CHAPTER  XXX 

QUINONES,   DYES  AND  INDICATORS    « 

Quinones.     These  may  be  regarded  as  diketones. 
The  best  known  of  them  is  benzoquinone  or  quinone, 

/co\' 

HC  CH 

which  has  the  structural  formula     ||  ||    ,   and 

HC  CH 

\CO/ 

may  be  prepared  by  oxidizing  various  para  deriva- 
tives of  benzene,  but  not  ortho  or  meta  derivatives. 
Thus  p-phenolsulphonic  acid,  p-sulphanilic  acid, 
p-amino-phenol,  etc.,  all  yield  quinone  when  oxidized. 
It  is  usually  prepared,  however,  by  oxidizing  aniline 
with  chromic  acid  or  by  oxidizing  hydroquinol: 

COH  C=0 


\  /\ 

C 


HC      CH          HC      CH 

|       ||     +0=    ||       ||     +H20. 
HC      CH          HC      CH 

v 

COH 


These  reactions  for  its  preparation  (with  the 
exception  of  its  preparation  from  aniline)  leave 
little  doubt  as  to  its  structural  formula. 

The  quinones  are  of  a  yellow  color  and  possess  a 

398 


QUINONES,  DYES  AND  INDICATORS  399 

pungent  odor.  In  some  particulars  they  behave 
like  ketones,  but  in  others  very  differently.  They 
have  oxidizing  properties  and  are  important  in  dye 
chemistry. 

INDICATORS 

At  this  stage  it  will  be  convenient  to  discuss 
briefly  the  theory  of  the  action  of  indicators. 

These  must  possess  weak  acid  or  basic  properties, 
and  be,  therefore,  undissociated  when  in  a  free  state, 
but  dissociated  when  present  as  salts.  In  the  dis- 
sociated state  the  anion  must  have  a  different  color 
from  that  of  the  undissociated  compound. 

Taking  the  three  most  commonly  used  indicators, 
phenolphthalein,  methyl  orange,  and  litmus,  let  us 
see  in  how  far  their  actions  can  be  thus  explained. 

(1)  Phenolphthalein.  This  is  of  the  nature  of  a 
very  feeble  acid,  so  that  it  is  undissociated  when  in 
a  free  state,  and  when  undissociated  it  is  colorless. 
When  dissociated,  however,  its  anion  has  a  red  color. 
Dissociation  occurs  when  it  is  converted  into  a  salt. 
Thus,  when  we  titrate  an  acid  with  sodium  hydrox- 
ide, using  phenolphthalein  as  indicator,  what 
happens  is  this:  In  the  presence  of  the  acid  the 
phenolphthalein  is  undissociated,  and  the  solution  is 
therefore  colorless;  as  alkali  is  added  the  acid 
becomes  gradually  neutralized,  until  at  last  a  trace 
of  alkali  in  excess  of  that  necessary  to  neutralize 
the  acid  is  present;  this  trace  combines  with  the 
phenolphthalein,  forming  a  salt,  which  then  dissoci- 
ates, so  that  the  anion  imparts  its  red  color  to  the 
solution. 


400  ORGANIC  CHEMISTRY 

The  acid  to  be  titrated  must  be  distinctly  stronger 
than  phenolphthalein,  for  otherwise,  before  the 
former  has  all  been  neutralized,  some  of  the  salt 
formed  will  become  hydrolyzed  (see  p.  70),  and  the 
base  thus  liberated  will  combine  with  the  phenol- 
phthalein and  form  a  salt  which,  partially  dissociat- 
ing, will  impart  a  pink  tint  to  the  solution.  Thus, 
phenols  cannot  be  titrated  with  phenolphthalein. 
On  the  other  hand,  such  a  feeble  acid  as  carbonic 
is  so  much  stronger  than  phenolphthalein  that 
the  latter  can  be  employed  as  an  indicator  for  titrat- 
ing it.  On  this  account  carbon  dioxide  (carbonates) 
must  be  absent  from  the  standard  alkali  used  for 
titrating.  Phenolphthalein  can  also  be  used  for 
practically  all  organic  acids. 

The  base  used  for  neutralization  must  also  be  a 
strong  one.  Thus,  if  a  feeble  base  such  as  ammonia 
is  employed,  then  the  salt  which  it  forms  with  the 
phenolphthalein  will  be  so  feeble  that  it  will  be 
decomposed  by  the  water  (hydrolysis),  and  the  end 
reaction  will  be  indefinite,  an  excess  of  ammonia 
requiring  to  be  present  before  the  decomposing 
effect  of  the  water  is  overcome.  Phenolphthalein 
must  not,  therefore,  be  used  when  ammonia  or 
ammonium  salts  are  present  in  a  solution. 

Phenolphthalein  is  the  ideal  indicator  for  weak 
acids  and  acid  salts,  and  should  be  employed  along 
with  a  strong  base. 

(2)  Methy1  Orange.  This  is  the  sodium  salt  of  a 
much  stronger  acid  than  phenolphthalein,  and  it 
dissociates  readily  in  weak  solution.  When  un- 
dissociated  (as  free  acid)  it  is  red,  when  dissociated 


QUINONES,  DYES  AND  INDICATORS  401 

(as  a  salt)  its  anion  is  yellow.  Its  dissociation  in 
water  is  prevented  by  the  presence  of  a  trace  of 
stronger  acid — such  solutions  are  therefore  red — 
but  if  alkali  is  added  in  sufficient  amount  just  to 
neutralize  this  acid,  then  the  methyl  orange  partially 
dissociates  and  the  solution  becomes  much  paler, 
and  if  a  trace  more  alkali  is  added,  still  more  dissocia- 
tion occurs,  so  that  the  solution  becomes  bright 
yellow.  Methyl  orange  is  not  affected  by  acid 
sodium  phosphate  (NaH2PO4),  so  that  a  weak  acid 
such  as  this  must  be  present  in  large  excess  before 
it  can  prevent  the  dissociation  of  methyl  orange; 
therefore,  for  titrating  acid  salts  this  indicator  is 
unsuitable;  and  for  the  same  reasons  it  cannot  be 
used  for  weak  organic  acids.  On  the  other  hand, 
it  is  suitable  for  practically  all  bases  and  carbonates, 
since  with  all  of  them  it  will  immediately  form  dis- 
sociable salts,  which  do  not  hydrolyze  so  long  as 
any  of  the  base  is  available  (i.e.,  uncombined  with 
the  acid  that  is  being  titrated,  which  must,  of 
course,  be  stronger  than  methyl  orange).  Nitrous 
acid  acts  on  methyl  orange  chemically,  therefore 
nitrites  must  not  be  present. 

Methyl  orange  is  therefore  especially  useful  for 
the  titration  of  bases,  including  ammonia,  and  un- 
suitable for  the  weaker  organic  acids.  Very  weak 
organic  bases  (as  aniline)  cannot  be  titrated. 

According  to  a  recent  theory  the  color  change  of 
phenolphthalein  and  methyl  orange  is  due  to  intra- 
molecular rearrangement  and  production  of  a  tau- 
tomer  having  a  quinoid  structure  (a  CH  group  of 
benzene  changed  to  CO).  For  example,  the  red 


402  ORGANIC  CHEMISTRY 

salt  of  phenolphthalein  (in  the  presence  of  dilute 
alkali)  is  said  to  have  the  following  quinoid  formula : 


Compare  this  with  the  formula  of  non-ionizing 
phenolphthalein  (p.  373). 

It  is  supposed  that  methyl  orange  has  a  tautomeric 
quinoid  structure  in  the  presence  of  free  acid.  The 
quinoid  substance  is  red  in  the  case  of  both  phenol- 
phthalein and  methyl  orange. 

The  indicators  used  for  the  detection  of  mineral 
acid  in  the  gastric  contents  belong  to  the  same  class 
as  methyl  orange,  e.g.,  Congo  red  (p.  410)  and  dimeth- 
ylaminoazobenzene  (p.  387).  While  it  is  true  that 
these  indicators  will  not  give  an  accurate  titration 
value  with  organic  acids,  our  experience  (contrary 
to  statements  in  clinical  chemistry  textbooks)  is 
that  methyl  orange,  Congo  red,  and  dimethyl- 
aminoazobenzene  give  a  distinct  color  reaction  (as 
with  mineral  acids)  even  when  used  with  very 
dilute  organic  acid  solutions  (see  exp.  p.  405).  The 
phloroglucin- vanillin  reagent  (p.  348),  however, 
reacts  only  to  mineral  acid  and  can  be  used  as  the 
indicator  when  making  a  quantitative  estimation  of 
mineral  acid  in  the  presence  of  organic  acids. 

(3)  Litmus.  This  stands  between  phenolphtha- 
lein and  methyl  orange  in  its  properties.  In  the 


QUINONES,  DYES  AND  INDICATORS  403 

un-ionized  state  it  is  red,  therefore  red  with  acids; 
and  in  the  ionized  state  blue,  therefore  blue  with 
alkalies. 

The  importance  to  the  student  of  thoroughly  understand- 
ing the  action  of  these  three  indicators  will  be  evident  from  a 
single  illustration,  namely  that  urine  reacts  very  differently 
towards  them.  Towards  methyl  orange  urine  (even  when  it 
is  acid  to  litmus)  reacts  alkaline  or  neutral,  towards  phenol- 
phthalein  it  reacts  acid,  while  towards  litmus  paper  urine 
reacts  acid  (usually),  neutral,  or  alkaline.  The  cause  of  this 
difference  in  action  lies  in  the  fact  that  in  this  fluid  we  have  a 
mixture  of  NaH2P04  and  Na2HP04.  Occasionally  these  two 
salts  are  present  in  equivalent  quantities  in  the  urine  (normally 
in  milk  also) ;  in  such  a  case  the  urine  reacts  acid  to  blue  litmus 
paper  and  alkaline  to  red  litmus  (amphoteric  reaction).  This 
is  due  to  the  fact  that  NaH2P04  is  acid  to  litmus,  and  Na2HP04 
is  alkaline.  In  normal  (acid)  urine  NaH2P04  preponderates 
over  the  alkaline  salt,  therefore  the  urine  reacts  acid  to  litmus. 
Even  the  acid-reacting  NaH2P04,  is  but  feebly  dissociated  (i.e., 
furnishes  few  ions)  compared  with  the  relatively  strong  acid  in 
methyl  orange;  therefore  it  is  unable  to  influence  the  degree  of 
dissociation  of  methyl  orange.  Congo  red  acts  in  the  same 
manner  as  methyl  orange.  Phenolphthalein,  however,  is  so 
feeble  an  acid  that  these  acid  salts  can  readily  keep  it  in  the 
(practically)  undissociated  condition  and  do  not  allow  the 
indicator  to  form  its  sodium  salt,  under  which  circumstances, 
as  we  have  already  stated,  it  remains  colorless. 

EXPERIMENTS.  (1)  Effect  of  ammonium  salts  on 
indicators,  (a)  Measure  with  a  pipette  5  c.c.  of 
decinormal  E^SCU  containing  ammonium  sulphate 
and  titrate  with  decinormal  NaOH,  using  methyl 
orange  as  indicator.  (6)  Repeat  (a)  but  use  phe- 
nolphthalein  as  indicator. 

(2)  Organic  acids,    (a)  Titrate  5  c.c.  of  decinormal 


404  ORGANIC  CHEMISTRY 

butyric  acid  with  methyl  orange;  (6)  with  phenol- 
phthalein. 

(3)  Acid  salts,  (a)  With  litmus  paper  (both  blue 
and  red)  test  solutions  of  NaH2P04  and  Na2HP04 
(both  being  one-tenth  gram  molecular),  then  mix 
4  c.c.  of  NaH2PO4  with  6  c.c.  of  Na2HP04,  and  test 
with  litmus  (amphoteric) .  (6)  Test  the  acidity 
of  acid  phosphate  to  methyl  orange  and  to  methyl 
red. 

Determination  of  the  H  ion  concentration  of  a 
solution  may  often  be  made  by  the  use  of  indicators. 
This  depends  on  the  fact  that  different  indicators 
suffer  a  color  change  in  the  presence  of  different 
degrees  of  acidity;  thus  rosolic  acid  gives  a  series 
of  colors  from  yellow  to  red  when  added  to  various 
solutions  of  low  acidity,  solutions  of  somewhat 
greater  acidity  give  colors  with  methyl  red  rang- 
ing from  red  to  yellow,  still  more  acid  solutions  give 
similar  color  changes  with  methyl  orange,  while 

N      N 

with  solutions  equivalent  to  — —  —  — —  HC1  Tropseolin 

1UU     oUU 

00  gives  a  gradation  of  colors  from  red  to  yellow 
(see  exp.  1). 

By  using  standard  solutions  of  known  H  ion 
concentrations  and  adding  the  proper  indicators, 
a  basis  is  secured  for  colorimetric  estimations.  To 
the  solution  to  be  tested  is  added  an  indicator 
which  gives  with  the  solution  one  of  the  intermediate 
colors  shown  by  the  standard  solutions  to  which 
the  same  indicator  has  been  added.  It  may  be 
necessary  to  try  several  indicators  before  the  right 
one  is  found.  The  final  determination  is  simply  a 


QUINONES,  DYES  AND  INDICATORS  405 

question  of  color  matching;  and  the  solution  is 
said  to  have  the  same  H  ion  concentration  as  the 
standard  solution  that  most  nearly  resembles  it  in 
color. 

EXPERIMENTS.  (1)  Select  12  test-tubes  having 
practically  the  same  diameter,  and  clean  them 
thoroughly,  rinsing  with  distilled  water.  Arrange 
them  in  three  series  of  four  tubes  each.  In  each  tube 
put  10  c.c.  of  the  acid  solution  indicated. 

For  series  1  use  |,  A,  ^,  and  JL  HCt. 


For  series  2  use  A,  _*L,  _*_  and  J^  lactic  acid. 


For  series  3  use  -j^  ^L,  gH_,  and  -^  lactic 
acid. 

To  each  tube  of  series  1  add  5  drops  of  .05% 
tropseolin  OO  (dissolved  in  50%  alcohol)  ;  for  series 
2  use  3  drops  of  .05%  alcoholic  solution  of  dimeth- 
ylaminoazobenzene  ;  and  for  series  3  use  3  drops 
of  .02%  methyl  orange.  After  mixing  note  the 
gradation  of  colors  obtained  in  each  series. 

(2)  In  order  to  illustrate  the  differing  H  ion 
concentrations  obtained  at  the  end-points  of  titra- 
tion  with  different  indicators,  titrate  successively 
5  c.c.  portions  of  one-tenth  gram  molecular  NaEbPC^ 
solution,  using  methyl  red,  rosolic  acid,  and  phenol- 
phthalein.  Explain  why  the  titrations  differ  so 
widely. 


406 


ORGANIC  CHEMISTRY 


DYES 

Several  of  these  have  already  been  mentioned. 
All  such  bodies  are  supposed  to  owe  their  dyeing 
properties  to  the  presence  in  them  of  a  so-called 
chromophore  group. 

Most  chromophore  groups  contain  double  link- 
ings.  The  azo  group  (N=N)  is  an  independent 
chromophore,  being  sufficient  of  itself  to  impart 
color  to  a  compound.  The  groups  C  =  0,  CH  =  CH 
and  N=C  are  dependent  chromophore  constituents, 
since  they  require  a  certain  environment  in  the  struc- 
ture of  the  molecule  in  order  to  enable  them  to 
impart  color;  the  true  chromophore  group  in  these 
cases  must,  therefore,  be  more  than  the  simple 
groups  given  above.  The  following  give  illustra- 
tions of  chromophore  groups: 

CO  CO 


QUINONES,   DYES  AND  INDICATORS  407 

The  presence  in  a  substance  of  one  of  these  groups 
alone  is  not,  generally,  sufficient  to  constitute  it  a 
dye,  the  substance  is  merely  a  chromogen;  certain 
other  groups,  such  as  OH  and  NEb,  must,  as  a 
rule,  be  attached  to  a  chromophore-containing  com- 
pound to  render  it  available  as  a  dye.  These 
assisting  or  auxiliary  groups  are  called  auxochromes; 
these  confer  salt-forming  properties.  The  auxo- 
chrome  has  the  effect  of  producing  color  in  color- 
less chromogens,  or  of  intensifying  the  color  of 
other  chromogens.  The  dye-stuff,  when  fully  elab- 
orated, will  have  basic  or  acidic  properties.  The 
sulphonic  acid  group  is  often  introduced  to  render 
a  dye  soluble  (and  acidic). 

In  solution  some  dyes  are  emulsoid  colloids,  a 
few  are  semi-colloids,  and  others  are  crystalloids. 
The  diffusible  dyes  can  penetrate  animal  tissues, 
and,  therefore,  can  be  used  as  stains  in  the  prep- 
aration of  tissues  for  microscopical  examination. 
The  semi-colloids  dialyze  slowly,  probably  because 
a  very  small  proportion  of  the  substance  is  in  true 
solution  in  equilibrium  with  that  portion  that  is  in 
colloidal  solution. 

If  cloth  is  immersed  in  water  its  fibers  acquire 
negative  charges  of  electricity.  Dyes  that  furnish 
electro-positive  ions  or  electro-positive  colloidal 
particles  are  adsorbed  by  the  fibers,  because  the 
ions  or  particles  are  attracted,  and  after  neutraliza- 
tion of  electrical  charges  are  precipitated  on  the 
fibers  (see  p.  95).  In  many  cases  the  amount  of 
dye  taken  up  from  a  solution  of  a  particular  concen- 
tration indicates  that  there  is  an  equilibrium  be- 


408  ORGANIC  CHEMISTRY 

tween  the  fibers  and  the  solution;  this  is  the  same 
sort  of  result  as  is  obtained  in  recognized  adsorption 
processes.  Dyes  that  have  electro-negative  ions 
or  colloidal  particles  may  be  adsorbed  by  fibers 
under  special  conditions,  for  instance,  when  elec- 
trolytes are  present. 

Basic  dyes  are  salts  of  weak  organic  bases  with 
strong  acids,  and,  therefore,  undergo  hydrolytic 
dissociation  (see  p.  70).  The  base  set  free  goes 
into  colloidal  solution,  the  particles  being  electro- 
positive. Acid  dyes  are  mostly  sodium  salts  of 
fairly  strong  organic  acids;  they  do  not  hydrolyze 
appreciably,  but  they  ionize.  The  ion  of  the  acid 
(electro-negative)  behaves  like  a  colloid. 

In  the  case  of  many  dyes  cotton  fibers  do  not  take 
up  the  color  satisfactorily.  Mordants  are  used  as  a 
preliminary  step  in  the  dyeing  process,  resulting  in 
the  coating  of  the  cotton  fibers  with  a  colloidal 
substance  which  is  capable  of  precipitating  or  adsorb- 
ing the  dye  substance.  For  basic  dyes  tannic 
acid  is  largely  used.  For  acid  dyes  acetates  of 
aluminium,  chromium,  and  iron  are  commonly 
employed,  the  cloth  being  soaked  with  the  acetate 
and  then  steamed  to  decompose  the  salt  and  leave 
the  colloidal  hydroxide  of  the  metal. 

In  some  cases  the  dye  may  enter  into  chemical 
combination  after  adsorption. 


CHAPTER  XXXI 

AROMATIC  COMPOUNDS  HAVING  CONDENSED 
RINGS 

Naphthalene  (CioH8)  contains  two  benzene  rings 
connected  in  the  following  manner: 


CH 


HC 


It  forms  white  crystals  melting  at  80°,  boiling  at 
218.1°  and  having  a  tar-like  odor.  It  is  volatile 
and  is  contained  in  coal-gas,  being  also  a  con- 
stituent of  the  distillate  from  coal-tar.  It  is  an 
antiseptic. 

EXPERIMENTS.  (1)  Heat  some  naphthalene  in  a 
sublimation  apparatus. 

(2)  Try  the  reaction  with  aluminium  chloride 
given  by  some  naphthalene  dissolved  in  chloroform 
(see  p.  332). 

The  naphthols,  CioHr-  OH,  correspond  to  phenols. 
Alpha-naphthol  (melting-point  95°)  and  beta-naph- 
thol  (melting-point  122°)  are  both  of  importance. 

409 


410  ORGANIC  CHEMISTRY 

a  Derivatives  of  naphthalene  have  some  group 
introduced  in  position  1,  4,  5  or  8,  while  0  derivatives 
have  it  in  position  2,  3,  6  or  7.  Ortho,  meta  and 
para  naphthalene  derivatives  have  two  substituting 
groups  attached  to  the  same  half  of  the  formula  (as 
inpositions  1,  2,  3,  4). 

Epicarin   is   /3-naphthol-ortho-hydroxy-toluic  acid, 

/COOH 
C6H3eOH 

xCH2-OCi0H7 

/3-Naphthol  benzoate,  d0H7  —  OOC-C6H5,  is  an- 
other of  the  newer  remedies. 

Orphol  is  bismuth  /3-naphtholate.  All  these  sub- 
stances are  antiseptics. 

Alpha-  and  beta-naphthylamines,  CioHr-NEk  are 
used  as  reagents.  a-Naphthylamine  is  used  to  detect 
the  presence  of  and  to  estimate  the  amount  of  traces 
of  nitrites,  as  in  drinking  water.  This  test  depends 
on  the  fact  that  a  red  compound,  azo-benzene- 
naphthylamine-sulphonic  acid,  is  produced. 

Congo  red  is  a  complex  diazonium  derivative  of 
naphthylamine-sulphonic  acid.  Its  formula  is 


Its  color  becomes  blue  in  the  presence  of  free  acids. 
It  forms  a  colloidal  solution,  which  will  not  dialyze. 
Electrolytes  cause  its  molecules  to  aggregate. 

Santonin,  CisHigOs,  is  a  naphthalene  derivative 
and  is  the  inner  anhydride  or  lactone  of  santonic  acid. 
Its  formula  is  probably, 


ANTHRACENE 
C_CH3    CH2 


411 


CH— CH3 


CH2 


Elaterin,  a  neutral  principle,  is  said  to  be  a  deriva- 
tive of  naphthalene. 

Anthracene.     CuHio,   is  a  hydrocarbon  contain- 
ing three  benzene  rings  condensed  together: 
CH  CH          CH 


or 


It  occurs  in  coal-tar  in  small  quantity  and  is  used  in 
manufacturing  alizarin.  Its  crystals  melt  at  216.5° 
(corrected).  Exposure  to  light  changes  it  into  dian- 
thracene,  which  depolymerizes  in  the  dark  to  anthra- 
cene, a  reversible  photo-chemical  reaction: 

^  C28-H20* 


412 


ORGANIC  CHEMISTRY 


One  of  the  important  derivatives  of  anthracene  is 
anthraquinone, 

CH  CO 


Dihydroxyanthraquinone  is  the  very  important  dye 
alizarin,  Ci4H602(OH)2: 

CH  CO  COH 


COH 


H 


CH  CO 

This  was  formerly  obtained  from  a  plant.  It  is 
now  produced  much  more  cheaply  by  synthetic 
means.  Its  synthesis  on  a  commercial  scale  is  one 
of  the  great  achievements  of  organic  chemistry. 

Aloin  is  an  anthraquinone  derivative.  Its  formula 
may  be  (the  position  of  the  OH  being  uncertain) : 


CH 


CO 


HO-C 


C-CH3 
CH3 

0— CH(CHOH)3CHO 


PHENANTHRENE  413 

Chrysophanic  acid,  Ci4H502(CH3)(OH)2,  and 
chrysarobin,  Ci5H1203,  are  anthracene  derivatives  of 
therapeutic  importance,  chrysophanic  acid  probably 
being  monomethyl-dihydroxy-anthraquinone,  and 
chyrsarobin  monomethyl-trihydroxy-anthracene. 

Emodin,  CisHioOs,  is  2-monomethyl  3,  6,  7-tri- 
hydroxyanthraquinone. 

Rhein,  CisHsOe,  is  also  an  anthraquinone  deriva- 
tive, 

/COOH  (1) 
(3)      . 


XOH  (5) 

Isomeric  with  anthracene  is  phenanthrene, 
CH  CH 


Some  chemists  think  that  it  may  be  a  derivative 
of  diphenyl,  the  two  benzene  rings  being  linked  to 
CH  =CH,  in  addition  to  the  direct  linking,  the  form- 
ula being  written: 


CHAPTER  XXXII 
HETEROCYCLIC  COMPOUNDS 

HETEROCYCLIC  compounds  are  related  to  the 
aromatic  compounds,  but  contain  at  least  one  atom 
other  than  C  atoms  in  the  ring;  this  is  generally  N.1 

Pyrrol    has    the  formula   HC — CH.    lodol  is   a 

HC    CH 


NH 

medicinal  derivative;  it  is  tetraiodopyrrol. 

1  Heterocyclic  compounds  of  minor  importance  are  thiophene, 
HC— CH 

HC    CH' 
\/ 

s 

pyrazole, 

HC— CH 

HC    NH 

\/ 
NH 
imidazole, 

HC— N 


YH 

and  furan, 

HC— CH 


v 

414 


HETEROCYCLIC  COMPOUNDS  415 

Pyrrolidine  is  the  hydrogen  addition  derivative  of 
pyrrol,  EbC  3    4  CH2.    This  is  the  basis  of  certain 

alkaloids. 


H2C 


2      5 


CH2 


NH 

Prolin  and  hydroxy-prolin  are  pyrrolidine  acids 
(p.  271). 

Haematin,  haemin,  and  haematoporphyrin  (from 
haemoglobin)  are  supposed  to  contain  four  pyrrol 
rings  in  their  molecules. 

Antipyrin  or  phenazone  is  an  important  derivative 
of  pyrazolone,  which  contains  the  pyrazole  ring, 
its  formula  being  : 

CH3 

N—  CH3. 
N—  C6H5 

It  is  an  antipyretic  of  value,  and  is  a  crystalline 
substance  melting  at  113°. 

Two  of  its  derivatives  are  used  as  remedies: 
pyramidon  or  dimethylamino-antipyrin,  and  tussol 
or  antipyrin  mandelate. 

Furfuraldehyde  is  the  chief  derivative  of  furan; 
its  formula  is 

HC=CH 

I      > 

HC=C^-CHO. 

Pyridine  Bases.  These  are  ammonia  deriva- 
tives and  of  great  importance  on  account  of  their 
relationship  to  certain  alkaloids  which  will  be  dis- 


416  ORGANIC  CHEMISTRY 

cussed   presently.     The    simplest   member   of   the 
series  is  pyridine,  which  has  the  structural  formula, 
CH 

HC/NCH 

.    It  may  therefore  be  considered  as 
'CH 

N 

benzene  with  a  CH  group  replaced  by  nitrogen 
(C5H5N).     There  are  several  methyl  pyridines. 

The  pyridines  are  contained  in  coal-tar,  and  are 
formed  when  bones  are  distilled,  being  produced 
by  the  action  on  one  another  at  high  temperatures  of 
acrolein,  ammonia,  methylamine,  etc. 

Pyridine  is  a  colorless  liquid  with  an  odor  like 
tobacco-smoke.  It  boils  at  115°  C.  It  mixes 
readily  with  water,  the  resulting  solution  being 
strongly  alkaline.  Like  other  tertiary  ammonia 
bases,  it  directly  combines  with  acids  to  form 
crystalline  salts.  When  it  is  warmed  with  alkyl 
halides,  addition  products  are  formed,  and  if  these 
be  treated  with  caustic  potash  a  very  pungent  and 
disagreeable  odor  is  evolved. 

EXPERIMENTS.  (1)  Dissolve  some  pyridine  in 
water;  test  alkalinity  with  litmus.  Notice  the 
odor. 

(2)  Then  neutralize  the  solution  with  HC1,  add  a 
few  drops  of  platinic  chloride  solution,  and  boil; 
a  yellow  precipitate  of  (CsHsN^PtCU  forms. 


HETEROCYCLIC  COMPOUNDS  417 


CONDENSED    HETEROCYCLIC    BENZENE    COM- 
POUNDS 

PYRROL  DERIVATIVES  OF  BENZENE 


/ 
Indol,     C6H4<        /CH,    contains     the     pyrrol 

nucleus,  condensed  with  the  benzene  nucleus,  and 
may  be  represented  thus  : 

CH  CH 


CH 


NH 


Skatol  is   methyl   indol,    C6H4<^       ^CH.       Indol 

and  skatol  are  contained  in  faeces,  imparting  the 
characteristic  odor  to  the  latter.  They  are  pro- 
duced in  the  intestine  by  the  action  of  bacteria  on 
the  aromatic  groups  (tryptophan)  in  protein.  They 
are  volatile  with  steam. 

Indican  is  the  oxidation  product  of  indol  in  com- 
bination with  sulphuric  acid  as  an  ethereal  sulphate, 

/  C  ^-0— S02(OK) 
CeH^        \CH  .      It    is    potassium    in- 

doxyl-sulphate.  It  is  sometimes  present  in  the 
urine  in  considerable  quantity.  The  urine  may  also 
contain  indoxyl  glycuronic  acid.  The  origin  of  these 


418  ORGANIC  CHEMISTRY 

bodies  is  indol  absorbed  from  the  bowel-contents. 
Indigo  can  be  obtained  from  it;  and  indigo  is  de- 
posited from  urine  containing  much  indican  after 
ammoniacal  decomposition  sets  in.  To  estimate  the 
indican  in  the  urine  it  is  converted  into  indigo  by 
various  reagents,  and  this  is  then  removed  by 
shaking  with  chloroform.  The  blue  chloroform 
solution  can  be  compared  with  an  indigo  solution 
of  known  strength,  and  thus  a  colorimetric  estima- 
tion may  be  made. 

Skatoxyl-sulphuric    acid    is    the    corresponding 

r^  _  OTT 

derivative  of  skatol,  C6H4/          C—  0—  S02(OH). 


C  ^-CH2.CH(NH2)  -COOH 


Tryptophan,    Ce 

is  /3-indol  a-amino-propionic  acid.  It  is  a  decom- 
position product  of  protein,  being  produced  during 
tryptic  digestion.  It,  in  turn,  is  attacked  by 
bacteria  in  the  intestines,  giving  rise  to  indol.  It 
gives  a  color  reaction  with  glyoxylic  acid  (see  p.  220). 

XCO\ 
Directly  related  to  indol  is  isatin,  CeH4<^         ">CO, 

dioxyindol,  for  the  former  can  be  obtained  from  the 
latter  by  reduction.  Indigo,  structurally,  is  a  com- 
bination of  two  isatin  molecules,  the  end  oxygen 
atom  of  each  molecule  being  eliminated,  thus  : 


Indigo  can  be  produced  from  isatin.     It  is  a  valu- 
able blue  dye.     The  synthesis  of  indigo  on  a  com- 


HETEROCYCLIC  COMPOUNDS  419 

mercial  scale  is  one  of  the  great  achievements  of 
chemistry.  Most  of  the  indigo  marketed  nowadays 
is  artificially  produced,  the  cost  of  manufacture 
being  only  about  one-fourth  the  cost  of  production 
of  natural  indigo.  It  will  be  of  interest  to  give  an 
outline  of  one  of  the  recent  commercial  methods. 
Naphthalene  is  the  starting-point  of  the  synthesis. 
This  is  oxidized  by  fuming  H2S04  to  phthalic  acid, 
and  the  latter  is  converted  into  phthalimide  by 
the  action  of  ammonia  gas;  then  by  treatment  with 
chlorine  and  caustic  soda  phthalimide  becomes 
converted  into  anthranilic  acid.  This  acid  is  con- 
densed with  monochloracetic  acid, 

COOH 
giving  .     Fusion    with    KOH 


NH 

splits  off  C02  and  water,  producing 

XXK 

CeEU^        /CH,  which  is  then  oxidized  in  alkaline 

solution  to  indigo  by  a  current  of  air. 

In  plants  the  indigo  is  contained  in  a  glucoside 
combination,  indican  (p.  253).  Reduction  (adding 
H)  changes  indigo  to  indigo  white;  it  is  in  this  form 
that  it  is  introduced  in  alkaline  solution  into  cloth 
for  dyeing;  on  exposure  to  air  it  oxidizes  to  the 
insoluble  indigo  blue.  Indigo  red,  indirubin,  is  a 
structural  isomer  of  indigo. 

EXPERIMENT.  Synthesize  indigo.  To  1  c.c.  of 
water  add  3  drops  of  acetone  and  a  few  crystals  of 
orthonitrobenzaldehyde.  Warm  the  mixture  in  a 


420  ORGANIC  CHEMISTRY 

bath  kept  at  50°  for  ten  minutes.  Cool,  add  a  few 
drops  of  10%  NaOH  and  shake.  A  yellow  color 
appears  first,  then  a  green.  When  it  is  deep  green 
add  chloroform  and  shake.  Indigo  dissolves  in  the 
chloroform  (blue  solution).  Remove  the  bottom 
layer  with  a  pipette,  and  run  it  into  a  sample  bottle. 
As  the  solvent  evaporates  indigo  is  deposited  on  the 
wall. 

CONDENSED    PYRIDINE-BENZENE    COMPOUNDS 

Quinoline  (chinoline)  is  another  tertiary  ammonia 
base.  It  may  be  considered  as  naphthalene  in  which 
a  CH  group  has  been  replaced  by  N: 


,C9H7N. 
CH 


It  is  found  in  coal-tar.  When  certain  alkaloids, 
particularly  quinine  and  cinchonine,  are  distilled 
with  potassium  hydroxide,  quinoline  is  obtained. 
Quinoline  can  be  synthesized  from  aniline  and 
glycerol  in  the  presence  of  nitrobenzene  and  concen- 
trated sulphuric  acid  (see  exp.  below):  The  reac- 
tions involved  are  as  follows:  the  glycerol  is  de- 
hydrated to  acrolein ;  removal  of  a  molecule  of  water 
from  acrolein  by  further  dehydration  causes  com- 
bination with  aniline  forming  acrolein-aniline; 
and  finally  oxygen  from  nitrobenzene  removes  a 
hydrogen  atom  from  the  end  of  the  chain  and  also 


HETEROCYCLIC  COMPOUNDS  421 

from  the  benzene  ring,  resulting  in  the  closing  of  the 
pyridine  ring. 

CH  CH2  CH  CH 

fCH 

+0='  +H20 


CH      HCUUCH 

CETN  CH    N 

(Acrolein-aniline)  (Quinoline) 

Quinoline  is  a  liquid  boiling  at  240°.  By  proper 
treatment  of  quinoline,  pyridine  can  be  derived  from 
it.  Many  alkaloids  are  quinoline  derivatives. 

Oxyquinoline  Sulphate (chinosol) ,  (CgHyNO)  2  EbSC^, 
is  a  substance  used  as  an  antiseptic,  and  is  said  to 
be  non-toxic. 

EXPERIMENT.  Synthesize  quinoline.  "  In  a  liter 
flask  mix  15  gm.  of  nitrobenzene,  24  gm.  of  aniline, 
and  75  gm.  of  glycerol;  add  62  gm.  of  C.P.  H2SO4 
while  agitating  the  mixture.  Connect  with  an  air- 
condenser  having  a  diameter  of  2  cm.,  and  heat 
the  flask  very  gradually  on  a  sand-bath.  Wrap  the 
condenser  with  a  damp  rag.  When  the  reaction 
begins  (sudden  bubbling)  remove  the  flame.  If  the 
action  is  very  vigorous,  cool  the  upper  part  of  the 
flask  with  an  air  stream  from  a  bellows.  When  the 
mixture  becomes  quiet,  heat  for  three  hours  on  a 
sand-bath.  Then  dilute  with  300  c.c.  of  water  and 
distill  with  steam.  When  no  more  oily  drops  of 
nitrobenzene  come  over,  stop  the  distilling.  Cool 
partially,  render  the  mixture  alkaline  with  strong 
NaOH  solution,  and  again  distill  with  steam,  thus 


422  ORGANIC  CHEMISTRY 

removing  the  quinoline  and  aniline.  This  last 
distillate  is  specially  treated  to  convert  the  aniline 
into  phenol,  as  was  directed  in  the  experiment  under 
phenol  (see  p.  338).  Diazotize  the  cooled  liquid 
after  rendering  it  distinctly  acid  with  dilute  H2S04, 
warm  in  a  bath,  make  alkaline  (the  phenol  becomes 
fixed  as  a  phenolate,  while  quinoline  is  set  free), 
and  distill  with  steam.  Extract  the  quinoline  from 
the  distillate  with  ether  and  proceed  just  as  was  done 
with  phenol. 

Thalline,  C9H9(OCH3)NH,  and 
Kairine,   C9H9(OH)N  —  C2H5,    are    quinoline  de- 
rivatives that  have  been  used  as  antipyretics. 

Analgen  (quinalgen)  is  a  more  recent  antipyretic, 
C9H5(OC2H5)NH(COC6H5)N. 

Kynurenic  acid,  occurring  in  the  urine  of  dogs,  is  a 
quinoline  derivative, 

CH  COH 

OH; 


N 

it  is  supposed  to  be  derived  from  tryptophan. 

Atophan  is  one  of  the  newer  remedies  that  is  of 
importance.     It  is  phenyl-quinoline-carboxylic  acid, 

CH  C—  COOH 


CH  N 


HETEROCYCLIC  COMPOUNDS  423 

Novatophan  is  the  ethyl  ester  of  methyl  atophan. 
Isoquinoline,  CgHyN,  is  an  isomer  of  quinoline: 
CH  CH 


CH  CH 

It  is  of  importance  because  of  the  derivation  of  many 
alkaloids  from  it.  The  formula  may  be  written  with 
N  at  any  one  of  the  four  positions  at  the  sides  of  the 

rings. 

SYNOPSIS 
Aromatic  Compounds 
A.  BENZENE  HYDROCARBONS. 
Benzene  derivatives. 

1.  Halogen  derivatives. 

2.  Hydroxy  derivatives. 

™       ,     (  Ethers. 
a.  Phenols  ]  _A,         .     ., 
(  Ethereal  salts. 

/i\  AT        -j    u       i    (Substitution 

(1)  Monacid  phenols  •< 

(      products. 

(2)  Diacid  phenols. 

(3)  Triacid  phenols. 

6.  Fatty  alcohol  side-chain  compounds  and  deriva- 
Alcohols. 
Aldehydes, 


tives 


Ketones. 

TV/T      L    •       -j    f  Salts. 

Monobasic  acids  •<  _  . 

/  Ethereal  salts. 


c.  Phenolic  monobasic  acids. 

3.  Dibasic  acids. 

4.  Nitrogen  derivatives. 

(a)  Nitro  compounds. 
(6)  Amino  compounds, 
(c)  Diazo  compounds. 


424  ORGANIC  CHEMISTRY 

5.  Sulphur  derivatives. 

6.  Arsenic  derivatives. 

7.  Quinones. 

B.  CONDENSED  BENZENE  RINGS. 

1.  Naphthalene. 

2.  Anthracene. 

3.  Phenanthrene. 

C.  HETEROCYCLIC  COMPOUNDS. 

1.  Pyrrol  and  pyridine  bases. 

2.  Condensed  heterocyclic-benzene  rings. 

(1)  Indol  and  derivatives. 

(2)  Quinoline  and  derivatives. 

(3)  Isoquinoline  and  derivatives. 

D.  ALKALOIDS. 


CHAPTER    XXXIII 

ALKALOIDS  AND. DRUG  PRINCIPLES 

ALKALOIDS 

IN  its  broadest  application  the  term  alkaloid 
includes  all  nitrogenous  organic  substances  that  are 
basic  in  character  (alkaloid  =  alkali-like) .  Caffeine 
and  theobromine,  purin  bases  and  other  leuco- 
maines,  choline,  muscarine,  and  ptomaines  have  all 
been  called  alkaloids. 

The  most  recent  definition  which  seems  acceptable 
is  that'alkaloids  include  all  nitrogenous  plant  prod- 
ucts which  have  N  in  a  closed  chain  of  atoms. 
Many  of  them  contain  more  than  one  N  atom  in  the 
molecule.  Most  alkaloids  are  tertiary  ammonia 
bases.  Those  the  structure  of  which  is  known  are 
derivatives  of  pyridine,  pyrrolidine,  quinoline,  iso- 
quinoline,  phenanthrene,  or  purin. 

The  empirical  formulae  of  the  chief  alkaloids  are 
as  follows: 

Coniine CgHiyN. 

Nicotine. CioHi4N2. 

Sparteine Ci5H26N2. 

Theobromine C7H8N402. 

Theophylline C7H8N402. 

Caffeine C8HioN402. 

Pelletierine C8H15NO. 

425 


426  ORGANIC  CHEMISTRY 


Pilocarpidine 

Hydrastinine  ......  CnHi3NO3. 

Pilocarpine  .......  CnHi6N202. 

Physostigmine  .....  Ci5H2iN3O2  (Eserine). 

Eseridine  .........  Ci5H23N3O3. 

Homatropine  ...... 

Sinipine  .......... 

Apomorphine  ..... 

Pipeline  ..........  Ci7Hi9N03. 

Morphine 

Cocaine 

Hyoscine  .........  Ci7H2iN04.  (Scopolamine). 

Atropine  ..........  C17H23N03  .  1 

Hyoscyamine  .....  Ci7H23N03    J 

Codeine  ..........  Ci8H2iNO3. 

Lobeline  ..........  Ci8H23N02. 

Thebaine  .........  Ci9H2iNO3. 

Cinchonine  .......  Ci9H22N20    1  T 

r>,.     i      •  i-  /^    TT    AT  r\       Isomers. 

Cmchomdme  ......  Ci9H22N2O 

Curarine  ..........  Ci9H26N2O. 

Sanguinarine  ...... 

Berberine  ......... 

Papaverine  ....... 

Quinine  ..........  C20H24N202  (Isomer,  Quinidine) 

Hydrastine  .......  C2iH2iNO6. 

Strychnine  ........  C2iH22N202. 

Narcotine  .........  C22H23N(>7. 

Colchicine  ........  C22H25NO6. 

Gelseminine  .......  C22H26N203. 

Yohimbine  ........  C22H28N2O3. 

Brucine  ..........  C23H26N2O4. 

Narceine 


ALKALOIDS  AND  DRUG  PRINCIPLES  427 


Jervine 

Veratrine 

Aconitine 

Ergotinine 

Ergotoxine 


Coniine  and  nicotine  are  the  only  important  alka- 
loids that  contain  no  oxygen  and  that  are  volatile 
liquids.  Sparteine,  pelletierine,  and  pilocarpidine 
are  liquids,  but  non-volatile.  All  of  the  alkaloids 
form  salts  with  acids  (see  p.  258);  these  salts  are 
very  much  more  soluble  in  water  and  alcohol  than 
the  free  alkaloids.  The  free  alkaloids,  on  the  other 
hand,  are  more  soluble  than  their  salts  in  the  immis- 
cible solvents  —  ether,  chloroform,  benzene,  and  amyl 
alcohol.  In  solution  some  of  the  alkaloids  are  dis- 
tinctly alkaline.  Most  of  the  alkaloids  are  optically 
active,  and  generally  Isevorotatory. 

All  alkaloids  are  precipitated  by  phosphomolybdic 
and  phosphotungstic  acids,  most  of  them  by  potas- 
sium mercuric  iodide  and  many  of  them  by  tannic 
acid. 

Many  of  the  alkaloids  are  extremely  poisonous, 
but  in  minute  doses  they  are  very  valuable  remedies. 

The  alkaloids  here  considered  are  of  vegetable 
origin.  They  are  present  in  plants  as  salts  of  various 
organic  acids  (e.g.,  citric,  malic,  and  tannic  acids). 

Methods  of  determining  the  constitution  of 
alkaloids.  By  violent  reactions  (e.g.,  fusing  with 
alkali,  heating  with  bromine  or  phosphoric  acid, 
or  distilling  with  zinc  dust)  the  molecule  may  be 
shattered,  so  that  as  a  result  of  the  reaction  a 


428  ORGANIC  CHEMISTRY 

stable  nucleus  is  found,  such  as  pyridine,  quinoline 
or  isoquinoline.  Methyl  ether  Unkings  of  alkaloids 
may  be  broken  up  by  heating  with  hydriodic  acid, 
and  from  the  methyl  iodide  formed  the  number  of 
methoxy  groups  (OCH3)  can  be  ascertained. 

Alkaloids  that  are  esters  can  be  hydrolyzed,  and 
the  products  of  hydrolysis  can  be  examined.  Hy- 
droxyl,  carboxyl  and  carbonyl  groups  are  readily 
determined.  In  the  case  of  a  few  alkaloids  the  struc- 
ture of  the  molecule  has  been  proved  by  synthesis. 

We  shall  consider  now  some  of  the  facts  that  are 
known  in  regard  to  the  structure  of  alkaloids. 

PYRIDINE  DERIVATIVES 

It  is  necessary  to  designate  the  positions  of  groups 
in  the  pyridine  ring  thus: 

CH(7) 
\JH(0) 


(a')HCL    JCHfa) 


Piperidine  is  the  simplest  derivative, 

CH2 


lJcH2" 


H2c 

NH 

Piperine  is  contained  in  pepper.     It  is  a  combina 
tion  of  piperidine  and  piperic  acid, 


ALKALOIDS  AND  DRUG  PRINCIPLES  429 

Coniine  is  dextro-^-propyl  piperidine, 

CH2 
H2C/NCH2 

H2cl      JcH— CH2  -  CH2  -  CH3 
NH 

Nicotine  is  a  pyrrol  derivative  (see  p.  414)  of 
pyridine  the  attachment  of  methyl  pyrrolidine  to 
pyridine  being  in  the  0  position  of  the  latter  and 
position  2  of  the  former: 


CH       H2C 


CH 


CH2 


HC 

CH  N 

CH3 

Coniine  and  nicotine  have  marked  similarities; 
both  are  volatile  liquids  having  a  strong  odor,  and 
both  are  very  poisonous.  Coniine  is  obtained  from 
hemlock-seed,  and  nicotine  from  tobacco.  Both  are 
strongly  alkaline  to  litmus.  In  tobacco  the  nicotine 
is  combined  with  malic  acid  and  citric  acid.  Syn- 
thetic a-propyl  piperidine  is  identical  with  coniine, 
except  that  it  is  optically  inactive.  Optically 
active  coniine  can  be  obtained  from  this  by  securing 
crystals  of  the  tartrate  of  coniine,  the  first  crop  of 
crystals  containing  only  dextroconiine.  This  was 
the  first  synthesis  (1886)  of  a  natural  alkaloid. 

Nicotine  is  laevorotatory.  d  Z-Nicotine  has  been 
synthesized;  from  this  the  I  variety  is  separated  by 


430  ORGANIC  CHEMISTRY 

crystallization  of  the  tartrate.  d-Nicotine  is  much 
less  toxic  than  Z-nicotine. 

Sparteine  is  thought  to  be  a  piperidine  derivative, 
but  its  chemical  structure  has  not  been  fully  deter- 
mined. It  is  dextrorotatory. 

The  artificial  alkaloids  a-  and  /3-eucaine  are  com- 
plex piperidine  bodies. 

C6H6COOvc/OOC.CH3      C6H 


H2(X    >CH< 
H3& 
H3C 


CH3  H 

(a-eucaine)  (3-eucaine) 

The  eucaines  are  local  anaesthetics,  and  differ  from 
cocaine  in  action  in  that  they  do  not  affect  the  pupil. 

Euphthalmine  is  related  to  /3-eucaine,  having  a 
CHa  group  in  place  of  the  H  attached  to  N  and  hav- 
ing the  mandelic  acid  radicle,  CeHs-CHOH-COO 
instead  of  the  benzoic  acid  radicle.  It  dilates  the 
pupil  more  quickly  and  less  persistently  than  atropin. 
It  is" not  an  anaesthetic. 

PYRROLIDINE  DERIVATIVES 

The  alkaloids  of  the  cocaine  and  atropine  group  are 
all  pyrrolidine  derivatives.  This  class  of  alkaloids 
is  of  great  pharmacological  importance.  Cocaine 
is  an  invaluable  local  anaesthetic,  while  members  of 
the  atropine  group  are  used  to  dilate  the  pupil. 
The  basal  substance  for  all  of  these  compounds  is 


ALKALOIDS  AND  DRUG  PRINCIPLES 


431 


tropine.    This  has,  as  will  be  noticed,  a  secondary 
closed  carbon  chain: 


This  double  ring  nucleus 
is  called  the  tropan  nucleus. 
It  may  be  looked  upon  as  a 
condensation  of  the  pyrrol 
with  the  pyridine  ring,  hav- 
ing N  and  the  two  neighbor- 
ing C  atoms  in  common  to 
the  two  rings. 

Tropic  acid  has  the  formula 


CH2 


CH 


CHa 


C6H-CHW)H  ' 
Atropine  is   the   tropine  ester  (tropine  being  an 
alcohol)  of  tropic  acid,  its  formula  being, 


HC 


CH 


CH, 


CH 


CH2 


CH2OH 
'C6H5 

Atropine  is  optically  inactive.     Its  physiological 
action  is  what  would  be  expected  of  d  Z-hyoscyamine. 


432 


ORGANIC  CHEMISTRY 


Hyoscyamine  is  laevorotatory.  d-Hyoscyamine  has 
a  different  degree  of  physiological  action.  Like 
other  esters,  atropine  and  hyoscyamine  can  be 
saponified.  Atropine  has  been  synthesized. 

Atropine  and  its  isomers  have  a  marked  pharma- 
cological action. 

Eumydrine  is  the  nitrate  of  methyl  atropine, 
CH3  and  NOs  attaching  to  the  N  atom  of  atropine, 
the  latter  changing  its  valence  to  five.  It  is  used  for 
the  same  purposes  as  atropine,  but  is  much  less  toxic. 

Homatr opine  is  an  artificial  alkaloid  prepared  by 
the  condensation  of  tropine  and  mandelic  acid  in 
ester  combination.  It  dilates  the  pupil  more 
promptly  and  less  persistently  than  atropine. 

Scopolamine,  also  called  hyoscine,  is  an  ester, 
consisting  of  tropic  acid  combined  with  scopolin, 
C8Hi3N02,  an  alcohol  derived  from  pyrrolidine.  It 
is  Isevorotatory.  It  is  used  to  cause  analgesia. 

If  in  tropine  an  H  atom  of  a  CEb  group  of  the  sec- 
ondary ring  be  replaced  by  COOH,  ecgonine  is  obtained : 

H2C| ,  C  Ha 


HC 


CHOH 


ALKALOIDS  AND  DRUG  PRINCIPLES 


433 


From  this  is  derived  cocaine,  which  is  the  methyl 
ester  of  benzoyl  ecgonine: 

H2C  | 1 C  Ha 


HC 


Cocaine  exists  both  as  d  and  as  /,  the  latter  having 
a  more  marked  action.  Cocaine  is  a  very  valuable 
local  anaesthetic.  Its  solution  cannot  be  sterilized 
by  heat,  because  it  hydrolyzes  readily,  yielding 
methyl  alcohol  and  benzoylecgonine. 

Besides  this  similarity  of  cocaine  to  atropine  in 
chemical  structure,  there  are  some  resemblances  in 
pharmacological  action. 

Tropacocaine  has  a  formula  similar  to  cocaine, 
but  has  CH2  instead  of  CH-COOCH3.  It  is  less 
toxic  than  cocaine  and  as  strongly  anaesthetic.  It 
has  little  effect  on  the  pupil.  ' 

Other  substitutes  for  cocaine,  namely,  novocaine, 
stovaine,  and  alypin  (see  p.  360)  have  been  previously 
mentioned. 

Nicotine  is  a  pyrrolidine  derivative  as  well  as  a 
pyridine  derivative  (see  p.  429). 


434 


ORGANIC  CHEMISTRY 


(X)HC 


QUINOLINE  DERIVATIVES 

The  chief  alkaloids  of  this  class  are  the  cinchona 
alkaloids.  The  following  formula  has  been  suggested 

CH2=CH— CH— CH— CH2  f or  cinchonine : 

Quinine  probably 
has  the  same  for- 
mula, except  that  an 
H  atom  at  the  posi- 
tion marked  (X)  is 
replaced  by  the 
m  e  t  h  o  x  y  group 
(OCRs). 

Cinchonine  is  dex- 
trorotatory, quinine 
Isevorotatory.  Cin- 
chonidine  is  the  Isevo- 
rotatory isomer  of 
cinchonine.  Quini- 
dine  is  the  dextro- 
rotatory isomer  of  quinine.  Quinine  is  important 
as  a  medicine.  It  is  very  bitter. 

Euquinine,  an  ester,  quinine  ethyl  carbonate,  is 
tasteless.  It  gives  full  quinine  action. 

Aristoquin  is  similar  to  euquinine.  It  is  diquinine 
carbonic  ester.  Its  action  is  the  same  as  that  of 
quinine,  but  ifc  has  none  of  the  disadvantages  of 
the  latter. 

Quinine  and  urea  hydrochloride,  a  crystalline 
double  salt,  is  very  soluble  and  is  suitable  for  sub- 
cutaneous injection,  being  non-irritating  and  even 
anaesthetic  locally. 


N 


ALKALOIDS  AND  DRUG  PRINCIPLES 


435 


Strychnine  and  brucine  are  believed  to  be  quin- 
oline  derivatives,  but  their  structure  has  not  been 
fully  worked  out. 

Both  strychnine  and  brucine  are  laevorotatory. 
Strychnine  is  much  used  as  a  medicine,  brucine  not 
at  all. 

ISOQUINOLINE  DERIVATIVES 

The  minor  opium  alkaloids,  papaverine,  narcotine, 
and  narceine,  also  hydrastine  and  berberine,  belong  to 
this  group.  These  alkaloids  are  therapeutically  of 
very  little  importance  (except  hydrastine).  Papav- 
erine has  the  simplest  structure;  it  is  tetramethoxy- 
benzylisoquinoline;  its  formula  is 


0— CH3 


CH 


436 


ORGANIC  CHEMISTRY 


Papaverine  has  been  synthesized. 
Hydrastine  probably  has  the  similar  but  more  com- 
plicated formula: 

OCH3 


0   C 


H2C 


0    C\ 


\/o    , 

CH          CH2 


Narcotine  is  believed  to  be  methoxyhydrastine, 
the  OCHs  group  taking  the  place  of  H  at  (X). 

Hydrastinine  is  an  alkaloid  prepared  by  oxida- 
tion of  hydrastine  with  nitric  acid.  It  has  a  much 
stronger  physiological,  action  than  hydrastine.  Its 

CH 


formula  is  H 


0 


CH=0 
NH— CH3, 


CH 


ALKALOIDS  AND  DRUG  PRINCIPLES  437 

the  side  chain  being  bent   so  as  to   point  out  its 
derivation  from  hydrastine. 

Narceine  has  a  somewhat  similar  formula,  but  it 
has  in  addition  a  benzoic  acid  group  and  several 
methoxy  groups. 

Berberine  has  a  still  more  complex  formula. 


Cotarnine,  C^HisNO^  is  an  oxidation  product 
of  narcotine,  as  hydrastinine  is  of  hydrastine.  Its 
formula  corresponds  to  the  isoquinoline  half  of  the 
narcotine  formula.  It  is  methoxyhydrastinine.  Its 
hydrochloride  is  called  stypticin,  and  the  phthalate 
is  called  styptol. 

Cotarnine  and  hydrastinine  have  very  similar 
physiological  action;  both  affect  the  circulatory 
system  in  such  a  way  as  to  lessen  haemorrhage. 
Cotarnine  is  much  less  expensive. 

PHENANTHRENE  DERIVATIVES 

These  are  morphine,  codeine,  and  thebaine,  all  of 
them  being  alkaloids  present  in  opium.  Derivatives 
of  morphine  artificially  produced  are  apomorphine, 
dionine,  heroine  and  peronine. 

Morphine  is  the  most  valuable  alkaloid  for  thera- 
peutic purposes  that  we  have.  Opium  contains 
about  10%  of  morphine.  Its  derivatives  are  much 
weaker  in  physiological  action. 

Its  constitutional  formula  is  supposed  by  some  to 
be: 


ORGANIC  CHEMISTRY 


HC 


C-OH   (X) 


Codeine  is  supposed  to  have  the  above  formula, 
with  CHs  substituted  for  the  H  of  the  OH  group  at 
X.  Thus  codeine  is  the  monomethyl  ether  of  mor- 
phine. Codeine  has  been  prepared  from  morphine 
by  treating  the  latter  with  methyl  iodode  in  the  pres- 
ence of  caustic  potash: 

Ci7Hi7NO(OH)2+CH3I+KOH  = 

(Morphine) 

=  Ci7Hi7NO(OH)(OCH3)  +KI+H20. 

(Codeine) 


ALKALOIDS  AND  DRUG  PRINCIPLES          439 

It  is  prepared  by  heating  a  mixture  of  morphine 
and  potassium  methyl  sulphate  (K(CH3)S04)  with 
alcoholic  KOH  (see  exp.). 

Both  morphine  and  codeine  are  laevorotatory. 

Thebaine  is  supposed  to  have  two  less  hydrogen 
atoms  attached  to  the  phenanthrene  nucleus,  and 
two  OCHs  groups  in  place  of  the  two  hydroxyls  of 
morphine. 

By  the  action  of  concentrated  mineral  acids,  a 
molecule  of  water  can  be  removed  from  morphine, 
producing  apomorphine: 

Ci7H19N03—  H2O  =Ci7Hi7NO2. 

(Morphine)  (Apomorphine) 

It  is  supposed  that  in  apomorphine  the  phenan- 
threne nucleus  is  condensed  with  methyl  piperidine. 
It  turns  green  after  long  standing. 

Other  derivatives  of  morphine  have  been  recently 
put  forward  as  therapeutic  agents. 

Dionine  is  the  hydrochloride  of  the  ethyl  ether  of 
morphine,  Ci7Hi7NO(OH)(OC2H5)  -HC1. 

Heroine  is  an  ester,  diacetyl  morphine, 


< 


Peronine  is  the  hydrochloride  of  the  benzyl  ether 
of  morphine 

Ci7Hi7NO(OH)(OCH2C6H5)  -HC1. 

EXPERIMENTS.  (1)  Test  solutions  of  morphine 
sulphate  and  quinine  sulphate  with  alkaloidal 
reagents,  such  as  phosphomolybdic  acid,  picric  acid, 


440  ORGANIC  CHEMISTRY 

iodine  potassium  iodide  solution,  mercuric  potassium 
iodide,  and  tannic  acid  solutions. 

(2)  Dissolve  quinine  in  dilute  H2S04,  and  notice 
the  fluorescence  of   the   quinine   bisulphate   solu- 
tion. 

(3)  Extraction  of  an  alkaloid.     To   10  grams  of 
tea  add  500  c.c.  of  water,  and  heat,  keeping  the  liquid 
barely  at  boiling  temperature  for  15  minutes.     Pre- 
cipitate tannin  from  the  filtrate  of  this  by  adding 
10%  lead  acetate,  a  drop  at  a  time,  until  no  more 
precipitate  forms.     Filter,  and  evaporate  to  about 
75  c.c.     Cool  the  solution,  and  if  it  is  turbid  filter 
again.     Extract  it  twice  by  shaking  with  two  por- 
tions of  15  c.c.  of  chloroform.     Dry  the  chloroform 
with    anhydrous  Na2S(>4.     Filter  through  a  small 
filter  into  an  evaporating  dish.     Let  the  chloroform 
evaporate  spontaneously,  then  examine  the  crystal- 
line character  of  the  caffeine  residue.     Remove  a 
little  of  it,  and  taste  it.     Dissolve  part  of  the  residue 
in  a  few  c.c.  of  hot  water  and  test  the  solution  with 
alkaloidal  reagents  (exp.  1). 

(4)  Produce  codeine.     Dissolve  1  gm.  of  morphine 
(pure  alkaloid)  and  0.6  gm.  potassium  methyl  sul- 
phate in  50  c.c.  of  pure  methyl  alcohol,  warming  and 
shaking.     Then  add   an  excess  of  powdered  KOH 
until  strongly  alkaline,   attach  a  reflux  condenser 
and  heat   in   a  water-bath    for   two    hours.     Add 
20  c.c.  of  water,  neutralize  with  HC1  and  distill  off 
all  volatile  materials  on  a  boiling  water-bath.     Cool, 
make    slightly    alkaline  with    ammonia  and  filter; 
transfer  to  a  separating  funnel,  and  shake  with  sev- 
eral portions  of  benzene.     Dry  the  combined  ben- 


ALKALOIDS  AND  DRUG  PRINCIPLES  441 

zene  extracts  with  calcium  chloride,  filter  into  an 
evaporating  dish,  and  evaporate  to  dryness  on  a 
water-bath.  Dissolve  part  of  the  residue  with  2% 
HC1,  warming  gently. 

Test  a  drop  of  the  solution  with  potassium  mer- 
curic iodide  solution.  Also  make  the  following 
test:  (a)  make  a  paste  of  some  ammonium  molyb- 
date  with  a  few  drops  of  C.P.  H2SO4;  on  adding  a 
drop  of  the  alkaloid  solution  a  blue  color  is  obtained, 
warm  if  necessary  to  develop  the  color;  (6)  to  a  few 
drops  of  the  solution  add  2  c.c.  of  H2S04  containing 
1  drop  of  formaline,  and  a  reddish-violet  color  ap- 
pears. These  two  tests  are  given  also  by  morphine, 
but  morphine  cannot  be  extracted  by  means  of 
benzene.  A  test  given  by  codeine,  but  not  by  mor- 
phine, is  this:  to  the  residue  in  the  evaporating 
dish  add  about  1  c.c.  of  20%  H2S04  and  warm,  a 
faint  pink  color  appears. 

This  method  of  synthesis  should  yield  considerable 
impure  codeine.  Crystals  can  be  obtained  by  dis- 
solving a  little  in  chloroform,  and  allowing  a  drop 
of  the  solution  to  evaporate  on  a  slide. 

PURIN  DERIVATIVES 

The  methyl  xanthins,  caffeine  and  theobromine, 
have  been  discussed  elsewhere  (p.  293). 

Theophylline  is  1,  3-  dimethyl-  2,  6-  dioxypurin, 
an  isomer,  therefore,  of  theobromine.  These  three 
alkaloids  can  be  prepared  synthetically.  All  are 
used  as  remedies. 

Pilocarpine  does  not  have  the  full  purin  nucleus, 
but  has  the  heterocyclic  ring  imidazol  (see  p.  414). 


442  ORGANIC  CHEMISTRY 

C2H5—  CH—  CH  -  CH2 

I        I  I 

OC       CH2       C—  N^- 

V  II 

O  HC—  W 

It  is  dextrorotatory.     It  has  a  marked  pharmaco- 
logical action. 

CERTAIN  ALKALOIDS   THAT  HAVE  NOT  BEEN 
CLASSIFIED 

The  following  indicates  what  is  known  about  the 
structure  of  aconitine  : 

OC-CH3 

C21H2,(OCH3)4(N05) 


Colchicine  is  given  the  formula: 

-COOCH3 


DRUG  PRINCIPLES  OF   UNKNOWN  STRUCTURE 

Cantharidin,  CioHi2O4,  is  an  acid  lactone,  derived 
from  either  benzene  or  cyclohexane. 
Picrotoxin,  CisHieOe. 
Picropodophyllin,  C23H2409  •  2H20. 


APPENDIX 


Note  to  the  Instructor.1  If  it  is  desired  to  shorten 
the  time  given  to  the  experiments,  we  should  advise 
omitting  the  following:  preparation  of  phenol  from 
potassium  benzene  sulphonate  (see  p.  392),  the 
diazonium  experiments  (see  p.  386),  preparation  of 
sulphanilic  acid  (see  p.  395),  of  quinoline  (see  p.  421), 
and  of  codeine  (see  p.  440). 

Diazonium  salt  may  be  prepared  as  a  demon- 
stration by  the  instructor. 

To  permit  of  using  one  apparatus  (as  a  Beckmann 
apparatus  or  a  combustion  furnace)  with  the  entire 
class,  we  should  suggest  dividing  the  class  or  a  section 
of  it  into  five  groups  of  three  or  four  men  each,  the 
men  of  each  group  working  together  on  a  particular 
experiment,  but  the  various  groups  performing 
different  experiments  on  the  same  day.  Thus,  one 
group  may  do  crystallization  and  melting-point 
experiments  (see  pp.  9,  10),  a  second  may  carry 
out  fractional  distillation  (see  p.  14)  and  boiling- 
point  determination  (see  p.  18),  a  third  may  make 

*We  can  recommend  as  valuable  books  for  reference  the 
textbooks  of  organic  chemistry  by  Holleman,  W.  A.  Noyes, 
Bernthsen,  and  Meyer  and  Jacobson,  the  laboratory  manuals 
by  Gattermann  (translated  by  Schober),  W.  A.  Noyes,  and 
Cohen,  and  "  Introduction  to  Physical  Chemistry,"  by  Walker. 

443 


444  APPENDIX 

specific  gravity  determinations  (see  p.  25),  a  fourth 
may  do  a  combustion  analysis  (see  p.  32),  and  a 
fifth  may  use  the  Beckmann  apparatus  (see  p.  62). 
Each  group  will,  of  course,  have  to  take  the  experi- 
ments in  a  different  order,  thus : 

Group  I,  Lessons  1,  2,  3,  4,  5. 
Group  II,  Lessons  2,  3,  4,  5,  1. 
Group  III,  Lessons  3,  4,  5,  1,  2. 
Group  IV,  Lessons  4,  5,  1,  2,  3. 
Group  V,  Lessons  5,  1,  2,  3,  4. 

Spellings.  We  have  retained  the  ending  "  ine  " 
in  the  case  of  amines  and  alkaloids,  with  the  idea 
of  indicating  by  this  means  the  organic  substances 
that  are  distinctly  basic  in  character. 

Formulce.  We  strongly  advise  that  the  learning 
of  empirical  formulae  by  the  student  be  discouraged, 
but  that,  on  the  other  hand,  the  student  be 
thoroughly  drilled  in  giving  structural  formulae. 

The  Student.  Many  students  need  advice  as  to 
the  proper  method  of  studying  chemistry,  since  some 
try  to  learn  it  by  rote.  Medical  students  should 
be  urged  to  retain  this  textbook  for  use  as  a  reference 
book  while  studying  biochemistry,  physiology,  path- 
ology, and  pharmacology. 


REFERENCE  TABLES 

TABLE  I 
SPECIFIC  GRAVITY  AND  PERCENTAGE  OF  ALCOHOL 

[According  to  Squibb.] 


Per 

Cent 
Alcohol 
by 
Volume. 

Per 

Cent 
Alcohol 
by 
Weight. 

SPECIFIC  GRAVITY. 

Per 
Cent 
Alcohol 
by 
Volume. 

Per 
Cent 
Alcohol 
by 
Weight. 

SPECIFIC  GRAVITY. 

At 
15.56° 

At 
25°  „ 
15.56 

At 
15.56° 
15.56 

At 
25° 

15.56  U 

15.56^ 

1 

0.79 

0.9985 

0.9970 

31 

25.51 

0.9643 

0.9594 

2 

1.59 

.9970 

.9953 

32 

26.37 

.9631 

.9582 

3 

2.39 

.9956 

.9938 

33 

27.23 

.9618 

.9567 

4 

3.20 

.9942 

.9922 

34 

28.09 

.9609 

.9556 

5 

4.00 

.9930 

.9909 

35 

28.96 

.9593 

.9538 

6 

4.80 

.9914 

.9893 

36 

29.83 

.9578 

.9521 

7 

5.61 

.9898 

.9876 

37 

30.70 

.9565 

.9507 

8 

6.42 

.9890 

.9868 

38 

31.58 

.9550 

.9489 

9 

7.23 

.9878 

.9855 

39 

32.46 

.9535 

.9473 

10 

8.04 

.9869 

.9846 

40 

33.35 

.9519 

.9456 

11 

8.86 

.9855 

.9831 

41 

34.24 

.9503 

.9438 

12 

9.67 

.9841 

.9816 

42 

35.13 

.9490 

.9424 

13 

10.49 

.9828 

.9801 

43 

36.03 

.9470 

.9402 

14 

11.31 

.9821 

.9793 

44 

36.93 

.9452 

.9382 

15 

12.13 

.9815 

.9787 

45 

37.84 

.9434 

.9363 

16 

12.95 

.9802 

.9773 

46 

38.75 

.9416 

.9343 

17 

13.78 

.9789 

.9759 

47 

39.67 

.9396 

.9323 

18 

14.60 

.9778 

.9746 

48 

40.60 

.9381 

.9307 

19 

15.43 

.9766 

.9733 

49 

41.52 

.9362 

.9288 

20 

16.26 

.9760 

.9726 

50 

42.52 

.9343 

.9267 

21 

17.09 

.9753 

.9719 

51 

43.47 

.9323 

.9246 

22 

17.92 

.9741 

.9706 

52 

44.42 

.9303 

.9226 

23 

18.76 

.9728 

.9692 

53 

45.36 

.9283 

.9205 

24 

19.59 

.9716 

.9678 

54 

46.32 

.9262 

.9184 

25 

20.43 

.9709 

.9668 

55 

47.29 

.9242 

.9164 

26 

21.27 

.9698 

.9655 

56 

48.26 

.9221 

.9143 

27 

22.11 

.9691 

.9646 

57 

49.23 

.9200 

.9122 

28 

22.96 

.9678 

.9631 

58 

50.21 

.9178 

.9100 

29 

23.81 

.9665 

.9617 

59 

51.20 

.9160 

.9081 

30 

24.66 

.9652 

.9603 

60 

52.20 

.9135 

.9056 

445 


446 


REFERENCE  TABLES 


TABLE  I— Continued 

[According  to  Squibb.] 


Per 

Cent 
Alcohol 
by 
Volume. 

Per 

Cent 
Alcohol 
by 
Weight. 

SPECIFIC  GRAVITY. 

Per 
Cent 
Alcohol 
by 
Volume. 

Per 

Cent 
Alcohol 
by 
Weight. 

SPECIFIC  GRAVITY. 

At 
15.56° 
15.56 

At 
25° 
15.56    ' 

At 
15.56° 
15.56 

At 
25° 
15.56 

61 

53.20 

0.9113 

0.9034 

81 

74.74 

0.8611 

0.8530 

62 

54.21 

.9090 

.9011 

82 

75.91 

.8581 

.8500 

63 

55.21 

.9069 

.8989 

83 

77.09 

.8557 

.8476 

64 

56.22 

.9047 

.8969 

84 

78.29 

.8526 

.8444 

65 

57.20 

.9025 

.8947 

85 

79.50 

.8496 

.8414 

66 

58.27 

.9001 

.8923 

86 

80.71 

.8466 

.8384 

67 

59.32 

.8973 

.8895 

87 

81.94 

.8434 

.8352 

68 

60.38 

.8949 

.8870 

88 

83.19 

.8408 

.8326 

69 

61.42 

.8925 

.8846 

89 

84.46 

.8373 

.8291 

70 

62.50 

.8900 

.8821 

90 

85.75 

.8340 

.8258 

71 

63.58 

.8875 

.8796 

91 

87.00 

.8305 

.8223 

72 

64.66 

.8850 

.8771 

92 

88.37 

.8272 

.8191 

73 

65.74 

.8825 

.8746 

93 

89.71 

.8237 

.8156 

74 

66.83 

.8799 

.8719 

94 

91.07 

.8199 

.8118 

75 

67.93 

.8769 

.8689 

95 

92.46 

.8164 

.8083 

76 

69.05 

.8745 

.8665 

96 

93.89 

.8125 

.8044 

77 

70.18 

.8721 

.8641 

97 

95.34 

.8084 

.8003 

78 

71.31 

.8696 

.8616 

98 

96.84 

.8041 

.7960 

79 

72.45 

.8664 

.8583 

99 

98.39 

.7995 

.7914 

80 

73.59 

.8639 

.8558 

100 

100.00 

.7946 

.7865 

The  table  of  the  U.  S.  Bureau  of  Standards  gives  specific  gravities 
for  a  number  of  concentrations  of  alcohol  differing  from  those  in  this 
table  by  0.0002  to  0.0005;  for  instance,  the  figures  for  95-100% 
alcohol  are  lower  by  0.0004-0.0006. 


REFERENCE  TABLES 


447 


TABLE  II 

MILLIGRAMS  OF  PURE  NITROGEN  IN  1  c.c.  OF  THE  MOIST  GAS 
AT  VARIOUS  TEMPERATURES  AND  UNDER  VARIOUS  PRESSURES 
(MILLIMETERS  OF  MERCURY) 


Tem- 

perature. 

721 

724 

727 

730 

733 

736 

739 

742 

10° 

1.130 

1.135 

1.139 

1.144 

.149 

1.154 

.158 

.163 

11 

.125 

1.129 

1.134 

1.139 

.144 

1.148 

.153 

.158 

12 

.120 

1.124 

1.129 

1.134 

.139 

1.143 

.148 

.153 

13 

.115 

1.119 

1.124 

1.129 

.134 

1.138 

.143 

.148 

14 

.110 

1.114 

1.119 

1.124 

.129 

1.133 

.138 

.143 

15 

.105 

1.109 

1.114 

1.119 

.124 

1.128 

.133 

.138 

16 

.099 

1.103 

1.108 

1.113 

.118 

1.123 

.127 

.132 

17 

.094 

1.098 

1.103 

1.108 

.113 

1.118 

.122 

.127 

18 

.089 

1.093 

1.098 

1.102 

.107 

1.112 

.116 

.121 

19 

.084 

1.088 

1.093 

1.097 

.102 

1.107 

.111 

1.116 

20 

.079 

1.083 

1.088 

1.092 

.097 

1.102 

.106 

1.111 

21 

.074 

1.078 

1.082 

1.087 

.091 

1.096 

.101 

1.106 

22 

.068 

1.072 

1.076 

1.081 

.086 

1.091 

.095 

1.100 

23 

.062 

1.067 

1.071 

1.076 

.080 

1.085 

.090 

1.094 

24 

.057 

1.061 

1.066 

1.071 

.075 

1.080 

.084 

1.089 

25 

.051 

1.056 

1.060 

.065 

.069 

1.074 

.078 

1.083 

26 

.046 

1.050 

1.054 

.059 

.064 

1.068 

.072 

1.077 

27 

.040 

1.044 

1.048 

.053 

.058 

1.062 

.066 

1.071 

28 

.034 

1.038 

1.042 

.047 

.052 

1.0C3 

.060 

1.065 

29 

.028 

1.032 

1.036 

.041 

.046 

1.050 

.054 

1.059 

30 

.022 

1.026 

1.031 

.035 

.040 

1.044 

.048 

1.053 

Tem- 

perature. 

745 

748 

751 

754 

757 

760 

763 

766 

10° 

1.168 

1.173 

.177 

.182 

1.187 

1.192 

.197 

1.202 

11 

1.162 

1.167 

.172 

.176 

1.181 

1.186 

.191 

1.196 

12 

1.157 

1.162 

.167 

.171 

1.176 

1.181 

.186 

.190 

13 

1.152 

1.157 

.162 

.166 

1.171 

1.176 

.181 

.185 

14 

1.147 

1.152 

.157 

.161 

1.166 

1.171 

.176 

.180 

15 

1.142 

1.147 

.152 

.156 

1.161 

1.166 

.170 

.175 

16 

1.137 

1.141 

.146 

.150 

1.155 

1.160 

.164 

.169 

17 

1.131 

1.136 

.140 

.144 

1.149 

1.154 

.158 

.163 

18 

1.125 

1.130 

.135 

.139 

1.144 

1.149 

.153 

.158 

19 

1.120 

1.125 

.130 

.134 

1.139 

1.144 

.148 

.153 

20 

1.115 

1.120 

.125 

.129 

1.134 

1.138 

.143 

.148 

21 

1.110 

1.114 

.119 

.123 

1.128 

1.133 

.138 

.142 

22 

1.104 

1.108 

1.113 

.117 

1.122 

1.127 

.132 

.136 

23 

1.098 

1.103 

1.107 

.111 

1.116 

1.121 

.126 

.131 

24 

1.093 

1.097 

1.101 

.106 

1.111 

1.116 

1.121 

.125 

25 

1.087 

1.092 

1.096 

.101 

1.105 

1.110 

1.115 

.119 

26 

1.082 

1.086 

1.090 

.095 

1.099 

1.104 

1.108 

.113 

27 

1.076 

1.080 

1.084 

.089 

1.093 

1.098 

1.102 

.107 

28 

1.070 

1.074 

1.078 

.083 

1.087 

1.092 

1.096 

.101 

29 

1.063 

1.068 

1.072 

1.077 

1.081 

1.086 

1.090 

.095 

30 

1.057 

1.062 

1.066 

1.071 

1.075 

1.080 

1.084 

.089 

448 


REFERENCE  TABLES 


TABLE  III 

SPECIFIC  GRAVITY  AND  PERCENTAGE  OF  NaOH  IN  AQUEOUS 
SOLUTION 


Specific 
Gravity 
at  15°. 

Per  Cent 
NaOH. 

Gm.  NaOH 
in  100  c.c. 

Specific 
Gravity 
at  15°. 

Per  Cent 
NaOH. 

Gm.  NaOH 
in  100  c.c. 

1.007 

0.61 

0.6 

1.220 

19.58 

23.9 

1.014 

1.20 

1.2 

1.231 

20.59 

25.3 

1.022 

2.00 

2.1 

1.241 

21.42 

26.6 

1.029 

2.71 

2.8 

1.252 

22.64 

28.3 

.036 

3.35 

3.5 

.263 

23.67 

29.9 

.045 

4.00 

4.2 

.274 

24.81 

31.6 

.052 

4.64 

4.9 

.285 

25.80 

33.2 

.060 

5.29 

5.6 

.297 

26.83 

34.8 

.067 

5.87 

6.3 

.    .308 

27.80 

36.4 

1.075 

6.55 

7.0 

.320 

28.83 

38.1 

1.083 

7.31 

7.9 

.332 

29.93 

39.9 

1.091 

8.00 

8.7 

.      .345 

31.22 

42.0 

1.100 

8.68 

9.5 

.357 

32.47 

44.1 

1.108 

9.42 

10.4 

1.370 

33.69 

46.2 

1.116 

10.06 

11.2 

1.384 

34.96 

48.3 

1.125 

10.97 

12.3 

1.397 

36.25 

50.6 

1.134 

11.84 

13.4 

.410 

37.47 

52.8 

1.142 

12.64 

14.4 

.424 

38.80 

55.3 

1.152 

13.55 

15.6 

.438 

39.99 

57.5 

1.162 

14.37 

16.7 

.453 

41.41 

60.2 

1.171 

15.13 

17.7 

.468 

42.83 

62.9 

1.180 

15.91 

18.8 

.483 

44.38 

65.8 

1.190 

16.77 

20.0 

.498 

46.15 

69.1 

1.200 

17.67 

21.2 

1.514 

47.60  ' 

72.1 

1.210 

18.58 

22.5 

1.530 

49.02 

75.0 

REFERENCE  TABLES 


449 


TABLE  IV 

SPECIFIC  GRAVITY  AND  PERCENTAGE  OF  KOH  IN  AQUEOUS 
SOLUTION 


Specific 
Gravity 
at  15°. 

Per  Cent 
KOH. 

Gm.  KOH 
in  100  c.c. 

Specific 
Gravity 
at  15°. 

Per  Cent. 
KOH. 

Gm.     KOH 
in  100  c.c. 

1.007 

0.9 

0.9 

1.252 

27.0 

33.8 

1.014 

1.7 

1.7 

1.263 

28.0 

35.3 

1.022 

2.6 

2.6 

1.274 

28.9 

36.8 

1.029 

3.5 

3.6 

1.285 

29.8 

38.5 

1.037 

4.5 

4.6 

1.297 

30.7 

39.8 

.045 

5.6 

5.8 

1.308 

31.8 

41.6 

.052 

6.4 

6.7 

1.320 

32.7 

43.2 

.06fr 

7.4 

7.8 

1.332 

33.7 

44.9 

.067 

8.2 

8.8 

1.345 

34.9 

46.9 

.075 

9.2 

9.9 

1.357 

35.9 

48.7 

.083 

10.1 

10.9 

1.370 

36.9 

50.6 

.091 

10.9 

11.9 

1.383 

37.8 

52.2 

.100 

12.0 

13.2 

1.397 

38.9 

54.3 

.108 

12.9 

14.3 

1.410 

39.9 

56.3 

.116 

13.8 

15.3 

1.424 

40.9 

58.2 

.125 

14.8 

16.7 

1.438 

42.1 

60.5 

.134 

15.7 

17.8 

1.453 

43.4 

63.1 

142 

16.5 

18.8 

1  ,468 

44.6 

65.5 

.152 

17.6 

20.3 

1.483 

45.8 

67.9 

1.162 

18.6 

21.6 

1.498 

47.1 

70.6 

1.171 

19.5 

22.8 

1.514 

48.3 

73.1 

1.180 

20.5 

24.2 

1.530 

49.4 

75.6 

1.190 

21.4 

25.5      . 

1.546 

50.6 

77.9 

1.200 

22.4 

26.9 

1.563 

51.9 

81.1 

1.210 

23.3 

28.2 

1.580 

53.2 

84.0 

1.220 

24.2 

29.5 

1.597 

54.5 

87.0 

1.231 

25.1 

30.9 

1.615 

55.9 

90.2 

1.241 

26.1 

32.4 

1.634 

57.5 

94.0 

450 


REFERENCE  TABLES 


TABLE  V 
ACETIC  ACID 


SPECIFIC  GRAVITY  AT  15°  OP 
VARIOUS  CONCENTRATIONS. 

FREEZING-POINT,  AS  AFFECTED 
BY  WATER-CONTENT. 

Per 

Cent  of 
Acetic 
Acid. 

Specific 
Gravity. 

Per 

Cent  of 
Acetic 
Acid. 

Specific 
Gravity. 

Per 

Cent  of 
Water. 

Freez- 
ing- 
point. 

Per 

Cent  of 
Water. 

Freez- 
ing- 
point. 

10.0 

1.014 

60.0 

1.069 

1.0 

14.8° 

5.6 

8.2° 

20.0 

1.028 

70.0 

1.073 

2.0 

13.25 

6.5 

7.1 

30.0 

1.041 

80.0 

1.075 

2.9 

11.95 

8.3 

5.3 

40.0 

1.052 

90.0 

1.071 

3.8 

10.5 

9.1 

4.3 

50.0 

1.062 

100.0 

1.055 

4.8 

9.4 

9.9 

3.6 

TABLE  VI 

VAPOR  TENSION  (AQUEOUS  PRESSURE  IN  MILLIMETERS  OF  MER- 
CURY) OF  WATER  AND  OF  40%  KOH  AT  VARIOUS  TEMPERA- 
TURES. 


Tem- 
pera- 
ture. 

Pure 
HtO. 

40% 
KOH. 

Tem- 
pera- 
ture. 

Pure 
H20. 

40% 
KOH. 

Tem- 
pera- 
ture. 

Pure 
H20. 

40% 
KOH. 

0 

4.6 

2.6 

12 

10.5 

5.8 

24 

22.2 

11.7 

1 

4.9 

2.8 

13 

11.2 

6.1 

25 

23.5 

12.4 

2 

5.3 

3.0 

14 

11.9 

6.5 

26 

25.0 

13.1 

3 

5'.7 

3.2 

15 

12.7 

6.9 

27 

26.5 

13.8 

4 

6.1 

3.4 

16 

13.6 

7.4 

28 

28.1 

14.7 

5 

6.5 

3.6 

17 

14.4 

7.8 

29 

29.8 

15.5 

6 

7.0 

3.9 

18 

15.4 

8.3 

30 

31.6 

16.4 

7 

7.5 

4.1 

19 

16.4 

8.9 

31 

33.4 

17.3 

8 

8.0 

4.4 

20 

17.4 

9.3 

32 

35.4 

18.3 

9 

8.6 

4.7 

21 

18.5 

9.9 

33 

37.4 

19.4 

10 

9.2 

5.1 

22 

19.7 

10.5 

34 

39.6 

20.5 

11 

9.8 

5.4 

23 

20.9 

11.1 

35 

41.9 

21.5 

REFERENCE  TABLES 


451 


TABLE  VII 
THE  DISSOCIATION  CONSTANTS  OF  CERTAIN  ORGANIC  ACIDS 


Substance. 

lOOtf. 

Substance. 

10QK. 

Formic. 

0  02140 

/3-Hydroxypropionic 

0  00311 

Acetic  

0.00180 

Lactic  

0  0138 

Propionic. 

0  00145 

Glyceric 

0  0228 

Butyric      

0  00175 

Malonic        .  .    . 

0  163 

Valerianic  

0.00156 

Succinic  

0  00665 

Caproic 

0  00147 

Glutaric 

0  00475 

Monochloracetic. 

0  155 

Tartaric 

0  097 

Dichloracetic 

5  144 

Benzoic 

0  006 

Trichloracetic.  .  .  . 
Monobromacetic 

120.00 
0  138 

o-Hydroxybenzoic, 
salicylic  

0  102 

Cyanacetic  
Glycollic  
Oxalic. 

0.370 
0.0152 
10  06 

ra-Hydroxybenzoic  .  . 
p-Hydroxybenzoic  .  . 
Phenol 

0.0087 
0.0029 
0  000000013 

TABLE  VIII 
DISSOCIATION  CONSTANTS  OF  CERTAIN  BASES 


Substance. 

IOOK. 

Substance. 

WOK. 

Ammonia  

0.0023 

Diethylamine    .  .  . 

0  126 

Methylamine   . 

0  050 

Trimethylamine 

0  0074 

Ethylamine.  

0.056 

Triethylamine 

0  064 

Dimethylamine  .  .  .  . 

0.074 

Benzylamine  

0  0024 

452 


REFERENCE  TABLES 


TABLE  IX 

THE  POWER  OF  CERTAIN  ACIDS  TO  CAUSE  HYDROLYSIS 


Acid. 

Inversion 
Coefficients 
(Cane- 
sugar)  . 

Velocity 
Coefficients 
(Methylace- 
tate). 

Velocity 
Coefficients 
(Acetamide). 

Hydrochloric  acid 

1  000 

1  000 

1  000 

Nitric  acid  

1  000 

0  915 

0  955 

Hydrobromic 

1  114 

0  983 

0  972 

Sulphuric  acid  

0.536 

0  541 

0  547 

Formic  acid 

0  0153 

0  0131 

0  00532 

Acetic  acid  

0  0040 

0  00345 

0  000747 

Monochloracetic  acid 

0  0484 

0  0430 

0  0295 

Dichloracetic  acid  

0  271 

0  2304 

0  245 

Trichloracetic  acid. 

'  0  754 

0  6820 

0  670 

Oxalic  acid  

0  1857 

0  1746 

0  169 

Succinic  acid. 

0  00545 

0  00496 

0  00195 

Citric  acid  

0  0172 

0  01635 

0  00797 

INDEX 


Absolute  alcohol,  142 
Acetaldehyde,  151 
Acetaldehyde  cyanhydrin,  147 
Acetamide,  274 
Acetaminophenetole,  382 
Acetanilide,  381 
Acetates,  165 
Acetic  acid,  161 

' '   ,  freezing-point      ta- 
ble, 450 
"  ,  glacial,  163 
"        ' '     metallic  salts,  165 
"        "  ,  mol.     wt.    determi- 
nation,    by    silver 
salt,  40 
"        "  ,  proofs  of  structural 

formula,  164 

•    "        "  ,  specific  gravity  ta- 
ble, 450 

"  >     "      tests,  163 
Acetic  anhydride,  169,  206 
Acetic  ether,  179 
Aceto-acetic  acid,  192,  218 
Acetone,  190 
Acetonitrile,  256 
Acetophenone,  355 
Acetozone,  352 
Acetphenetidin,  382 
Acetylation,  169,  206 
Acetyl  chloride,  166 
Acetylene,  304 
Acetylenes,  304 
Acetyl  group,  166 

' '       paraminophenyl     salicy- 

late,  367 
' '       salicylic  acid,  367 


Acetyl  value,  206 
Achroodextrin,  250 
Acid  amides,  115,  273 

"    chlorides,  166 

"    imides,  284 

"    strength,     estimation     of, 
183,  184 

"    value,  205 
Acids,  113 

"    ,  aromatic,  356 

' '    ,  dibasic  aromatic,  371 

11   ,  fatty,  157 

"    ,  H  ion  concentration  of, 
405 

' '    ,  monobsic  aromatic,  356 

"    ,  monobasic,    dibasic,  etc., 
113 

"    ,  strength  of,  172 
Aconitine,  427,  442 
Acrolem,  302 
Acrylic  acid,  302 
Acrylic  aldehyde,  302 
Acyclic  compounds,  116 
Acyl  halogenides,  166 
Adenin,  293 
Adrenalin,  383 
Adsorption,  95,  209,  407 
Agar-agar,  251 
Agaric  acid,  222 
Agaricinic  acid,  222 
Airol,  370 
Alanin,  268 
Alcohol,  absolute,  142 

' '       ,  denatured  or  methylat- 
ed, 142 

' '       ,  heat  of  combustion,  137 


453 


454 


INDEX 


Alcohol,  ordinary,  141 

"       ,  specific  gravity  tables, 

445 
Alcohols,  109 

' '       ,  aromatic,  349 

"       ,  diacid,  193 

**       ,  monacid,  diacid,  etc., 

112 

' '       ,  monacid  primary,  138 
"       ,  oxidation  products  of, 

112 

"       ,  primary,  110,  136 
11       ,  secondary,  110,  189 
"       ,  tertiary,  110,  192 
"      ,  triacid,  199 
Aldehyde,  151 

acid,  219,  221 
1          ammonia,  147 
'          bisulphite,  147 
'          group,  113 

tests,  147,  153 
Aldehydes,  112,  146 

"        ,  aromatic,  349 
Aldohexose,  231 
Aldol,  151 

Aldol  condensation,  151 
Aldose,  228,  231 
Aliphatic    division    of    organic 

chemistry,  103 
Alizarin,  412 

Alkaloidal  precipitants,  427 
Alkaloid,  extraction  of,  440 
Alkaloids,  425 

,  determination  of 
chemical  structure  of, 
427 

Alkyl  cyanides,  256 
"     hydroxides,  136 
"     halides,  124 
Alkyls,  108 
Allantoin,  292 
Alloxan,  287 
Alloxuric  bodies,  293 
Allyl  alcohol,  302 

' '    isothiocyanate,  307 
"   radicle,  302 


Allyl  sulphide,  307 

"   sulphocarbamide,  308 

"   thiourea,  308 
Aloin,  412 

Alpha  naphthol,  409 
Alpha  naphthylamine,  410 
Alphozone,  198 
Alypin,  360 
Amicrons,  87 
Amido  acids,  266 
Amido  group,  114 
Amines,  258 
Amines,  mixed  aromatic  fatty, 

379 

Aminoacetic  acid,  268 
Aminoacetphenetidin,  383 
Amino  acids,  114,  234,  266 
Aminoazobenzene,  387 
Aminobenzoic  acids,  360 
Amino  compounds,  aromatic,  376 
!3-Aminoethysulphonic  acid,  272 
Aminoformic  acid,  266 
a-Aminoglutaric  acid,  269 
Aminohexose,  233 
a-Aminoisobutylacetic  acid,  269 
Aminophenols,  382 
a-Aminopropionic  acid,  268 
Aminosuccinic  acid,  269 
Aminoiso valeric  acid,  269 
Ammonia  derivatives,  114 
Ammonium  carbamate,  266 
Ammonium  cyanate,  278 
Amphoteric  electrolytes,  267 
Amphoteric  reaction,  403 
Amygdalin,  252,  351 
Amyl  alcohol,  fermentation,  144 
"     '"      ,  inactive,  145 
"       "      ,  normal,  144 
Amylene  hydrate,  145 
Amyl  nitrite,  265 
Amylodextrin,  250 
Amylopectinj  250 
Amyloid,  ^246 
Amylose,  250 
Amylum,  249 
Amyl  valerate,  187 


INDEX 


455 


Ansesthesin,  367 
Anaesthetics,  125,  128,  133 
Analgen,  422 
Analysis,  elementary,  28 
Anhydrides,  169,  198,  371 
Anhydrolysis,  255 
Anilides,  381 
Aniline,  376 

' '       derivatives  of,  378 

"      salts,  377 
Anions,  66 
Anisole,  340 
Anozol,  131 
Anthracene,  411 
Anthracene  oil,  318 
Anthranilic  acid,  383 
Anthraquinone,  412 
Antifebrine,  381 
Antikamnia,  381 
Antinosin,  372 
Antipyretics,  381,  415 
Antipyrin,  415 
Antipyrin  mandelate,  415 
Apiol,  347 
Apomorphine,  439 
Aqueous  pressure,  450 
Arabinose,  229 
Arachidic  acid,  187 
Arbutin,  252 
Arginase,  270 
Arginin,  270 
Aristol,  131,  344 
Aristoquin,  434 
Aromatic  acids,  356 

' '        alcohols,  349 

"        amines,  376 

"        bases  having  nitrogen 
in  nucleus,  414 

"        compounds,    103,    116, 
316 

1 '        compounds,        having 

condensed  rings,  409 

Aromatic  compounds,   synopsis 

of,  423 

reactions 

of,  317 


Aromatic  hydroxy    compounds, 

336 

ketones,  354 
' '        nitrogen      derivatives, 

374 

' '        sulphur  derivatives,  391 
Arsacetin,  397 
Arsanilic  acid,  397 
Arseno-benzol,  396 
Arsine,  substitution  derivatives 

of,  264 
Aseptol,  393 
Asparagin.  277 
Asparaginic  acid,  269 
Aspartic  acid,  269 
Aspirin,  367 
Association  of  liquids,  69 

"       "  molecules   of   so- 
lute, 69 

Asymmetric  N  atom,  216 
Asymmetric  carbon  atom,  216 
Atomic  weight  of  elements  in 

organic  compounds,  2 
Atophan,  422 
Atoxyl,  397 
Atropine,  431 
Autocatalysis,  219 
Auxochromes,  407 
Avogadro's  hypothesis,  42 
Azobenzene,  388 

Baeyer's  reagent,  301 
Baking  powder,  224 
Ballistite,  201 
Balsams^SS 
Balsam  of  Peru,  358 
"      ofTolu,  358 
Barfoed's  reagent,  241 
Barometer,  correction  for  tem- 
perature, 20 
Bases,  strength  of,  172 
Bassorin,  251 

Beckmann's  thermometer,  60 
Beer,  see  Malt  liquors. 
Beet  sugar,  243 
Behenic  acid,  187 


456 


INDEX 


Benzal  chloride,  351 

Benzaldehyde,  351 

Benzamide,  361 

Benzanilide,  382 

Benzene,  318 

derivatives,  116,  316 
"        diazonium  nitrate,  384 
' '         diazonium      sulphonic 

acid,  395 

"      ,  di  substitution       prod- 
ucts of,  326 

"      ,  homologues  of,  329 

model,  Collie's,  324 

' '      ,  preparation  of,  320 

ring,.  323 

"      ,  structure  of,  320 
"         sulphonic  acid,  392 
"        trisubstitution  deriva- 
tives, 328 

Benzeugenol,  347 

Benzidine,  388 

Benzine,  121 

Benzoates,  358 

Benzoic  acid,  330,  356,  386 
' '      "      ,  preparation  of,  358 
"      "    ',  salts  of ,  358 
"      "      ,  substitution  prod- 
ucts of,  359 

Benzoic  aldehyde,  351 

Benzoin,  352 

Benzol,  318 

Benzonitrile,  386 

Benzophenone,  354 

Benzoquinone,  398 

Benzosol,  345 

Benzosulphinide,  394 

Benzotrichloride,  357 

Benzoylacetyl  peroxide,  352 

Benzoylaminoacetic  acid,  360 

Benzoyl  anilide,  382 

Benzoyl  chloride,  359 

Benzoylation,  359 

Benzozone,  352 

Benzyl  acetate,  350 

Benzyl  alcohol,  349 

Benzyl  chloride,  334 


Benzyl  methyl  ether,  350 

Berberine,  437 

Betaine,  261 

Beta  naphthol,  409 

Beta  naphthylamine,  410 

Betol,  368 

Bicyclic  compounds,  310 

Biological  methods  for  test- 
ing molecular  concentration, 
54 

Bitter  almonds,  oil  of,  351 

Biuret,  280 

Biuret  reaction,  280,  296 

Bleier  and  Kohn,  vapor  den- 
sity determination,  44 

Blood,  depression  of  freezing- 
point,  64 

Boiling-point  determination,  18 
at  760  mm.,  19 

Borneol,  313 

Boyle's  law,  41 

Branched  chains,  105,  123 

Brandy,  140 

Bromobenzene,  333 

Brometone,  192 

Bromoform,  129 

Bromural,  283 

Brownian  motion,  88 

Brucine,  435 

Butane,  105,  120 

Butter,  203,  204 

Butyl  alcohol,  normal,  144 

Butyl  chloral  hydrate,  156 

Butyric  acid,  185 

Butyrin,  186,  200,  203 

Butyrolactone,  219 

Cacodylic  acid,  264 

Cadaverine,  263 

Caffeine,  294,  441 

Camphor,  312 

"        ,  artificial,  311 
"          monobromide,  313 
,  oil,  347 

Camphoric  acid,  313 

Cane  sugar,  241,  243 


INDEX 


457 


Cantharidin,  442 

Caoutchouc,  314 

Capillarity,  73 

Capri  c  acid,  187 

Caprin,  203 

Caproic  acid,  187 

Caproin,  203 

Caprylic  acid,  187 

Caprylin,  203 

Caramel,  244 

Caraway,  oil  of,  344 

Carbamic  acid,  266 

Carbamide,  277 

Carbinol,  138 

Carbohydrates,  227 

Carbolic  acid,  337 

Carbolic  oil,  318 

Carbon  atom,  asymmetric,  216 
* '       ,  detection  of,  3 
' '       ,  estimation  of,  28 
oxychloride,  128 
11         tetrachloride,  120 

Carbonyl  group,  113 

Carboxyl  group,  113 

Carboxylic  acids,  157 

Carnitine,  262 

Carvacrol,  313,  343 

Castor  oil,  204,  304     ' 

Catalytic  action,    161,  179,  240, 
249 

Catalysis,  179 

Cataphoresis,  91 

Catechol,  345 

Cathode,  66 

Cations,  66 

Celloidin,  248 

Celluloid,  248 

Cellulose,  246 

Cellulose  nitrates,  247 
esters,  247 

Centric  benzene  formula,  323 

Cephalin,  262 

Ceryl  alcohol,  192 

Cetyl  alcohol,  192 

Cetyl  palmitate,  192 

Chemical  equilibrium,  175 


Chemical  structure,  how  deter- 
mined, 6 

Chinoline,  420 

Chinosol,  421 

Chloracetic  acids,  170 

Chloral,  154 

Chloral  alcoholate,  154 

Chloralamide,  156 

Chloral  formamide,  156 

Chloral  hydrate,  154 

Chloralose,  156 

Chloral  substitutes,  156 

Chlorbenzene,  333,  385 

Chlorbenzoic  acids,  334,  360 

Chlorbenzyl  alcohol,  350 

Chloretone,  191 

Chlorhydrins,  200 

Chlorine,  detection  of,  5 

Chloroform,  127 

11  acetone,  191 

"          ,  as  reducing   agent, 

238 

11          ,  molecular      weight 
determination,  44 

Chlorpropionic  acids,  185 

Chlortoluenes,  334 

Cholalic  acid,  220 

Cholesterine,  315 

Cholesterol,  315 

Cholic  acid,  220 

Choline,  261 

Chromophore  group,  406 

Chrysarobin,  413 

Chrysophanic  acid,  413 

Cinchonidine,  434 

Cinchonine,  420,  434 

Cineol,  314 

Cinnamic  acid,  362 

Cinnamic  aldehyde,  353 

Cinnamon  oil,  354 

Citrates,  226 

Citric  acid,  226 

Closed  carbon  chains,  309 

Cloves,  oil  of,  347 

Coal  gas,  119 

Cocaine,  433 


458 


INDEX 


Codeine,  438 
Cod  liver  oil,  204 
Coefficient  of  dissociation,  68 
Colchicine,  442 
Collargol,  97 

Collie's  benzene  model,  324 
Collodion,  248 

Colloidal  solutions,  79,  210,  407 
Colloids,  79,  210,  249,  407 
'        ,  irreversible,  83 
'        ,  precipitation  of,  92 
1        ,  protective,  96 
'        ,  reversible,  84 

,  swelling  of,  97,  211 
Combustion  analysis,  28 

analysis,     modified 
when      halogens 
present,  36 
analysis,     modified 
when    nitrogen 
present,  35 
analysis,     modified 
when     sulphur 
present,  36 
"  furnace,  30 

Condensation,  231,  234 
Condensed  benzene  rings,  409 
Conductivity,  electrical,  65 
Conglomerates,  216 
Congo  red,  402.  410 
Coniine,  429 
Constants,  60 
Constitutional      formula,      see 

Structural. 
Copper  acetate,  166 
Copper  acetylide,  305 
Copper-zinc  couple,  118 
Cordite,  201 
Cotarnine,  437 
Cream  of  tartar,  224 
Creatin,  285 
Creatinin,  285 
Creolin,  343 
Creosols,  346 
Creosote,  346 
Creosote  oil,  318 


Cresols,  343 
Cresylic  acid,  343 
Croton  chloral,  156 
Crotonic  acid,  303 
Croton  oil,  204 
Crystallization,  7 
Cryoscopy,  59 
Crystals,  purity  of,  10 
Cyanacetic  acid,  257 
Cyan  acids,  257 
Cyanamide,  278 
Cyanic  acid,  257,  278 
Cyanides,  114,  256 

"        ,  aromatic,  393 
Cyanpropionic  acids,  197 
Cyclic  compounds,  309 
Cyclopentane,  309 
Cyclopropane,  309 
Cy close,  310 
Cymene,  310,  332 
Cymogene,  121 
Cystein,  272 
Cystin,  272 
Cytosin,  295 

Dalton's  law,  41 

Definition  of  organic  chemis- 
try, 1 

Denatured  alcohol,  142 

Depression  of  freezing-point  by 
solutions,  59 

Dermatol,  370 

Destructive  distillation,  162 

Developers,  photographic,  345 

Dextrin,  141,  249,  260 

Dextroconiine,  429 

Dextrolactic  acid,  217 

Dextrose,  231,  238 

Diabetes,  238 

Diacid  phenols,  345 

Dialkyl  sulphides,  306 

Dialuric  acid,  290 

Dialysis,  22,  85 

Diamino  -  dihydroxy  -  diarseno 
(di)  benzene,  396 

Dianthracene,  411 


INDEX 


459 


Diastase,  141 
Diazoaminobenzene,  387 
Diazoamino  compounds,  387 
Diazo  compounds,  384 
Diazonium  salts,  384 
Diazotizing,  338 
Dibasic  aromatic  acids,  371     . 
Dibrommethane,  127 
Dichloracetic  acid,  170 
Dichlorhydrin,  200 
Dichlormethane,  127 
Diethyl  oxalate,  273 
Diffusion  of  colloids,  85 
Digitalin,  253 
Digitalose,  230,  253 
Digitonin,  253 
Digitoxin,  253 
Digitoxose,  230,  253 
Diglyceride,  207 
Dihydroxy  ace  tone,  228 
Dihydroxyanthraquinone,  412 
Dihydroxybenzoic  acid,  368 
Dihydroxydibasic  acids,  222 
Dihydroxy  monobasic  acids,  219 
Dhydroxyphenylacetic  acid,  371 
Dihydroxy  toluene,  347 
Dihydroxystearic  acid,  207 
Diiodoform,  131 
Diiodomethane,  127 
Diiodomethyl  salicylate,  366 
Diketones,  398 
Dimethylamine,  261 
Dime  thy  laminoazobenzene,  387, 

402 
Dimethylaminoazobenzene-sul- 

phonic  acid,  395 
Dimethylaniline,  380 
Dimethyl  xanthin,  293 
Dinitrobenzene,  375 
Dionine,  439 
Dioses,  228 
Dioxyindol,  418 
Dipalmito-olein,  204 

"         stearin,  204 
Dipeptides,  297 
Diphenylamine,  380 


Diphenylaminoazobenzene-sul- 

phonic  acid,  396 
Diphenylketone,  354 
Disaccharides,  228,  240 
Dissociation,  coefficient  of,  68 
Dissociation  constants  of  acids, 

451 
"  "  of  bases, 

451 

,  electrolytic,  65 
,  hydrolytic,  70,  209 
Distil  ation,  destructive,  162 
,  fractional,  13 
,  steam,  16 
,  vacuum,  16 
Disuccinyl  peroxide,  198 
Dithymol  diiodide,  344 
Dormiol,  156 
Drug  principles,  442 
Dulcitol,  232 

Dumas,    vapor    density    deter- 
mination, 43 
Duotal,  345 
Dyes,  406 

Dynamic  bonds,  323 
Dynamite,  201 

Ecgonine,  432 

Egg   membrane,   osmotic   pres- 
sure, 57 

Eka-iodoform,  131 

Elaterin,  411 

Electrical  conductivity  of  solu- 
tions, 65 

Electrolytes,  65 

Electrolytic  dissociation,  65 

Elements  in  organic  compounds, 
2 

Emodin,  413 

Empirical  formula,  6,  98 

Emulsin,  246,  252,  351 

Emulsions,  80 

Emulsoids,  81 

Enzymes,  141,  180 

Enzymes,  adsorption  of,  95 
"       ,  as  colloids,  95 


460 


INDEX 


Eosin,  373 
Epicarin,  410 
Epinephrin,  383 
Equilibrium,  chemical,  175 

of  ions  and  mole- 
cules, 68 
Ergotinine,  427 
Ergotoxine,  427 
Erucic  acid,  303 
Erythrodextrin,  250 
Eseridine,  426 
Eserine,  426 
Esterification,  174 
Esters,  173 
Ester  value,  206 
Ethanal,  151 
Ethane,  104,  120 
Ethene,  300 
Ethereal  salts,  166,  178 
Ethers,  109,  132 

,  aromatic  fatty,  340 

,  mixed,  134 

,  true  aromatic,  340 
Ethyl  acetate,  182 

alcohol,  139 

amine,  260 

benzene,  330 

benzoate,  359 

bromide,  125 

butyrate,  187 

carbamate,  267 

carbonate,  278 

chloride,  125 

cyanide,  255 

ether,  132 

glycollate,  213 

nitrite,  265 

sulphonic  acid,  306 

sulphuric  acid,  127 
Ethylene,  193,  300 

"        bromide,  193 

"  "    •   i  preparation 

of,  301 

11        lactic  acid,  214 
Ethylenes,  300 
Eucaine,  a  and  /3,  430 


Eucalyptol,  314 
Eucalyptus  oil,  314 
Eudoxine,  372 
Eugenol,  347 

' '        acetamide,  347 

"         carbinol,  347 

iodide,  347 
Eumydrine,  432 
Euquinine,  434 
Euthalmine,  430 
Exalgin,  382 
Extraction,  20 

Fats,  203 
' '   ,  vegetables,  204 

Fatty  acids,  157 

"      "    ,  volatile,  204 
"     compounds,   synopsis  of, 
115 

Fat  values,  205 

Fehling's  solution,  241 

Fermentation,  237,  240 

Fire  damp,  118 

Fischer,  Emil,  297 

Flashing  point  of  oils,  122 

Fluidity,  78 

Fluoresceiin,  372 

Formaldehyde,  148 

Formaline,  148 

Formamide,  274 

Formic  acid,  158 

et       "      series,  158,  187 

Formonitrile,  256 

Formula,  calculation  from  per- 
centage composition,  38 

Formulae,  empirical  and  struc- 
tural, 98 

Fractional  crystallization,  218 

Fractional  distillation,  13 

Freezing-point  constants,  60 

' '  depression  by  so- 

lutions, 59 

Fructose,  231,  235,  238 

Fruit  sugar,  238 

Fuchsin,  379 

Fuchsin,  acid,  379 


INDEX 


461 


Fuchsin  aldehyde  reaction,  148 
Furan,  414 

Furfuraldehyde,  230,  415 
Furfurol,  230,  415 
Fusel  oil,  145 

Galactose,  231,  238,  246,  251 

test,  246 

Galactosamine,  233 
Gallic  acid,  368 
Gallisin,  244 
Gall-nuts,  368 
Garlic,  oil  of,  307 
Gas,  coal,  119 

"  laws,  41 

"  ,  natural,  119 
Gases,     molecular    weight    of, 

41 

Gasoline,  121 
Gasoline,  fuel  value,  122 
Gastric  juice,  184,  402 
Gaultherin,  252 
Gay-Lussac's  law,  41 
Gelatine  dynamite,  201 
Gelose,  251 
Gelseminine,  426 
Glucoproteins,  233 
Glucosamine,  233 
Glucosazone,  235 
Glucose,  231,  236,  238 
d-Glucose,  a  and  /3,  236 
Glucosides,  251 
Glucosides,  artificial,  253 
Glucosone,  236 
Glutamic  acid,  269 
Glutamin,  277 
Glutaminic  acid,  269 
Glutaric  acid,  195 
Glutol,  149 

Glyceric  acid,  202,  219,  234 
aldehyde,  228,  234 
Glycerine,  199 
Glycerol,  199 

Glycerophosphoric  acid,  202 
Glycerose,  228 
Glyceryl  acetates,  206 


Glyceryl  butyrate,  200 
"        tribenzoate,  360 
11        trioleate,  203 
"        tripalmitate,  203 
"        tristearate,  203 

Glycin,  268 

Glycinamide,  275 

Glycocoll,  220,  268,  360 

Glycocholic  acid,  220 

Glycogen,  88,  250 

Glycol,  193 

"      aldehyde,  228 

Glycolates,  194 

Glycollates,  213 

Glycollic  acetate,  213 
"        acid,  194,  212 
aldehyde,  194 

Glycollid,  214 

Glycuronates,  paired,  221 

Glycuronic  acid,  221,  233,  237 

Glyoxal,  194 

Glyoxylic  acid,  194,  219 

Gram  molecular  solution,  50 

Gram  molecule,  42 

Grape  sugar,  238 

Green  soap,  209 

Guaiacol,  345,  346 

' '        benzoate,  345 

Guanidin,  284 

Guanin,  293 

Gum  Arabic,  251 
"     benzoin,  358 

Gums,  251 

Gum  tragacanth,  251 

Guncotton,  247 

Giinzberg's  reagent,  348,  402 

Gutta  percha,  315 

Hsematin,  415 
Hsematoporphyrin,  415 
Haemin,  415 
Haemoglobin,  298 
Halides,  108 

Halogens,  detection  of,  4,  5 
Halogen  derivatives  of  paraffins, 
124 


462 


INDEX 


Halogen  derivatives  of  benzenes, 

333 

Headache  medicines,  381 
Heat  of  combustion,  121,  137 
Heavy  oil,  318 
Hedonal,  283 
Helianthin,  395 
Heptoses,  240 
Heroine,  439 
Heterocyclic    compounds,    116, 

414 

Hexabasic  acid,  373 
Hexachlorbenzene,  333 
Hexamethylentetramine,  264 
Hexane,  104,  120,  123 
Hexone  bases,  270 
Hexoses,  231 
Hippuric  acid,  360 
Histidin,  271 
Holocain,  382 
Homatropine,  426,  432 
Homogentisic  acid,  371 
Homologous  series,  104 
Homologues  of  benzene,  329 
Hydrastine,  436 
Hydrastinine,  436 
Hydrazine,  388 
Hydrazobenzene,  388 
Hydrazones,  148,  235,  352 
Hydrion,  172 
Hydrocarbons   102 

' '  aromatic,  316 

cyclic,  309 

' '  groups  of,  102 

11  saturated,      103, 

117 

"  ,  unsaturated,  103, 

299 

Hydrocinnamic  acid,  362 
Hydrocyanic  acid,  256 
Hydrogels,  84 
Hydrogen,  detection  of,  3 
1 '        ,  estimation  of,  28 

ion       concentration, 

404 
"       ,  nascent,  118 


Hydrogenation  of  oils,  303 
Hydrolysis,  157 

•"         ,  power    of   acids    to 

cause,  452 

Hydrolytic  dissociation,  70,  209 
Hydrometer,  24 
Hydroquinol,  346 
Hydroquinone,  346 
Hydrosols,  84 
Hydroxion,  172 
Hydroxyacetic  acid,  212 
Hydroxy  acids,  114,  212 
Hydroxybenzoic  acids,  363 
/3-Hydroxybutyric  acid,  218 
Hydroxy  camphor,  313 
Hydroxy  compounds,   aromatic, 

336 

Hydroxycymenes,  344 
/3-Hydroxyethyl-sulphonic  acid, 

306 

Hydroxyformic  acid,  212 
Hydroxy hydroquinol,  348 
Hydroxyl  group,  nature  of,  136 
Hydroxyl,  test  for,  136,  146 
Hydroxy prolin,  271,  415 
Hydroxypropionic  acids,  214 
Hydroxytoluenes,  343 
Hyoscine,  426,  432 
Hyoscyamine,  432 
Hypertonic  solutions,  55 
Hypnal,  156 
Hypnone,  355 
Hypotonic  solutions,  55 
Hypoxanthin,  292 

Ichthyol,  307 

Identification  of  substances,  22, 

26 

Illuminating  gas,  119 
Imidazole,  414 
Imido  compounds,  284 
Imido  group,  114 
Indican,  253,  417,  419 
Indicators,  399 
Indigo,  418 
Indigo  red,  419 


INDEX 


463 


Indigo,  synthesis  of,  419 
"     ,  white,  419 

Indirubin,  419 

Indol,  417 

Indolaminopropionic  acid,  418 

Indoxylglycuronic  acid,  417 

Indoxylsulphuric  acid,  417 

Ink,  370 

Inosite,  310 

Inversion,  240 

Invertases,  240 

Invert  sugar,  241,  245 

lodal,  130 

Iodine,  dextrin  test,  250 
' '     ,  glycogen  test,  251 
'  *     ,  starch  test,  249 

Iodine  value,  206 

lodobenzene,  333 

lodoform,  129 

lodoformin,  131 

lodoformogen,  131 

lodol,  131.  414 

lodothyrin,  298 

lonization,  65 

"          constants,  451 
"          experiment,  342 
"          of  indicators,  399 

Ions,  65 
' '    ,  electrical  charge  of,  66 

Isatin,  418 

Isethionic  acid,  306 

Isoamyl  alcohol,  primary,  144 
11     ,  tertiary,  145 
"       acetate,  179 

Iso-butane,  123 

Isobutyl  alcohol,  144 
"        carbinol,  144 

Isobutyric  acid,  185 

Isocholesterol,  315 

Iso-compounds,  106,  123 

Isocyanide  reaction,  257 

Isocyanides,  256 

Isocyclic  compounds,  116 

Isoleucin,  269 

Isomaltose,  237,  244 

Isomerism,  98,  106 


Isomerism,  stereo-chemical,  214 
Isomers,  98 
Isonitriles,  256 
Isosmotic  solutions,  56 
Iso-paraffins,  123 
Iso-pentane,  123 
Isopral,  156 

Isopropylmetacresol,  344 
Isopropylorthocresol,  344 
Isoquinoline,  423 
Isosuccinic  acid,  198 
Isotonic  coefficient,  57 

"       solutions,  55 
Iso valeric  acid,  187 

Jervine,  427 

Kairine,  422 
Kekule',  322 
Kerosene,  121 
Ketohexose,  232 
Ketone  acid,  192 
Ketones,  114,  189 

"      ,  aromatic,  354 

11      ,  mixed  aromatic  fatty, 

354 
Ketose,  228,  231,  235 

"     test,  239 
Kjeldahl's  method  of  nitrogen 

estimation,  38 
Koprosterol,  315 
Kynurenic  acid,  422 

Lacmoid,  346 
Lactic  acid,  139,  214,  234 
Lactid,  218 
Lactocaramel,  244 
Lactones,  219 
Lactophenin,  382 
Lactosazone,  239 
Lactose,  240,  242,  244 
Lactylphenetidin,  382 
Lsevolactic  acid,  217 
Lsevulose,  231,  235,  238 
Lanolin,  192,  211 
Lard,  203 


464 


INDEX 


Laurie  acid,  187 
Lead  acetate,  165 

"      "       ,  basic,  165 

' '  ,  sugar  of,  165 
Lecithin,  262 
Leucin,  269 
Leucomaines,  295 
Light  oil,  318 
Lignin  test,  247 
Ligroin,  121 
Linoleic  acid,  304 
Litmus,  402 
Lobeline,  426 

Lowering  of  freezing-point,  59 
Lubricating  oil,  122 
Lycetol,  264 
Lysidin,  264 
Lysin,  270 
Lysol,  343 

Malic  acid,  221 
Malonic  acid,  197 
Malt,  141 

"     liquors,  140 
Maltodextrin,  250 
Maltosazone,  239 
Maltose,  141,  237,  240,  242,  244 
Mandelic  acid,  362 
Mannose,  231 
Maple  sugar,  243 
Marsh  gas,  see  Methane. 
Marsh  gas  series,  117 
Mass  action,  175 
Melissic  alcohol,  192 
Mellite,  373 
Mellitic  acid,  373 
Melting-point  determination,  10 
Menthol,  313 
Mercaptans,  115,  306 
Mesitylene,  330 

"         ,  preparation  of,  331 
Mesitylenic  acid,  362 
Mesotartaric  acid,  223 
Mesoxalic  acid,  222 
Meta  compounds,  326 
Metadihydroxybenzene,  346 


Metaldehyde,  151 
Metasulphobenzoic  acid,  394 
Metaxylene,  362 
Methanal,  148 
Methane,  104,  118 
Methane  series,  117 
Methoxyhydrastine,  436 
Methyl,  108 
Methyl  acetanilide,  382 
Methyl  acetate,  179 
Methyl  alcohol,  138 
Methylamine,  261 
Methylaniline,  378 
Methylated  alcohol,  142 
Methyl  carbinol,  139 
chloride,  125 

'        cyanide,  255 

'        ether,  132 

ethyl  ether,  135 

'        glycocoll,  268 

'        guanidin,  285 

'        guanin,  293 

'        hexoses,  231 
indol,  417 

'        isocyanide,  256 

'        orange,  395,  400 
Methylene  blue,  396 
Methyl  pentoses,  230 
Methylphenylhydrazine,  235 
Methylphenyl  ketone,  355 
Methyl  pyridines,  416 

"      salicylate,  364 

' '       thionin     hydrochloride, 
396 

"      violet,  380 

"      xanthins,  293 
Meyer,  Victor,  method,  44 
Microns,  87 
Milk  sugar,  244 
Models    representing    formulae, 

106 
Models  to  represent   stereoiso- 

merism,  223 
Mole,  42 
Molasses,  243 
Molecular  disperse  solutions,  80 


INDEX 


465 


Molecular  weight: 

Calculated      from     freezing- 
point  determination,  64 
Calculated  from  osmotic  pres- 
sure, 50 

Calculated  from  vapor  den- 
sity determination,  41 
Determined   by    analysis    of 

derivatives,  40 

Determination  by  depression 
of  freezing-point,  59 

Molecular  weight  of  gases  and 
vapors,  41 

Molecular  weight  of  colloids,  90 

Molisch's  test,  234,  254 

Monobasic  acids,  40,  113 

Monobromethane,  125 

Monobromisovaleryl-urea,  283 

Monochloracetic  acid,  170 

Monochlorethane,  125 

Monochlorhydrin,  200 

Monochlormethane,  125 

Monoformin,  160 

Monohydroxybenzene,  336 

Monohydroxybenzoic  acids,  363 

Monohydroxy dibasic  acids,  221 

Monohydroxytribasic  acids,  226 

Monomethyldihydroxyanthra- 
quinone,  413 

Monomethyltrihydroxyanthra- 
quinone,  413 

Mononitrobenzene,  374 

Mononitrophenol,  341 

Monosaccharides,  227 

"  ,  general    reac- 

tions of,  235 

Mordants,  408 

Morphine,  437 

Mucic  acid,  233 

Multirotation,  236 

Murexide,  291 

Muscarine,  262 

Mustard  oil,  307,  343 

Mutarotation,  236 

Mycoderma  aceti,  161 

Myristic  acid,  187 


Naphtha,  121 

Naphthalene,  409 

Naphthols,  409 

/3-Naphthol  benzoate,  410 

a-Naphthol-orthohydroxytoluic 
acid,  410 

Naphthylamines,  410 

Naphthylamine-sulphonic    acid, 
410 

Narceine,  437 

Narcotine,  436 

Nascent  hydrogen,  118 

Natural  gas,  119 

Neo-pentane,  123 

Neurine,  264 

Neuronal,  283 

Nicotine,  429 

Nirvanin,  367 

Nitriles,  acid,  256 

Nitrites,  265 

Nitrobenzene,  374 

Nitrobenzoic  acids,  360 

Nitrocellulose,  247 

Nitro-compounds,  264 

' '  ,  aromatic,  374 

Nitroparaffins,  264 

Nitrogen    derivatives  of  paraf- 
fins, 114,  255 
' '        ,  detection  of,  3 
"         ,  estimation    by    com- 
bustion, 36 
"         ,  estimation   by    Kjel- 

dahl's  method,  38 
tables,  447 

Nitroglycerine,  201 

Nitroglycerol,  201 

Nitrophenols,  341 

Nitrous  acid,  action  on  amines, 
260 

Non-electrolytes,  65 

Nonoses,  240 

Normal  compounds,  106 

Nosophen,  372 

Novaine,  262 

Novaspirin,  367 

Novatophan,  423 


466 


INDEX 


Novocaine,  360 
Nucleic  acid,  295 
Nuclein  bodies,  293 
Nucleoproteins,  295 

Octoses,  240 

Oil  of  bitter  almonds,  351 

caraway,  344 

cinnamon,  354 

cloves,  347 

eucalyptus,  314 

garlic,  307 

peppermint,  313 

sassafrass,  347 

thyme,  332 

turpentine,  311 

wintergreen,  365 
Olefiant  gas,  300 
Olefins,  300 
Oleic  acid,  303 
Olein,  203 
Oleomargarine,  186 
Oieo-palmito-stearin,  204 
Olive  oil,  204 
Opium  alkaloids,  435,  437 
Optical  activity,  216 
Optical  activity  of  protein  de- 
composition products,  271 
Orange  II,  395 
Orangine  powders,  381 
Orcein,  347 
Orcin,  347 
Orcinol,  347 
Organic     chemistry,     definition 

of,  1 
Organic  chemistry,  preliminary 

survey  of,  101 
Organic  compounds,  synopsis  of, 

115 
Organic  substances,  solvents  of, 

7       . 

Ornithin,  270 
Orphol,  410 
Ortho  compounds,  326 
Orthodihydroxybenzene,  345 
Orthoform,  367 


Orthophthalic  acid,  371 

Osazones,  235,  238,  245 

' '        ,  melting-points  of,  239 

Osmotic  cell,  48,  49 

Osmotic  pressure,  46 

Osmotic  pressure  of  colloids,  90 

Osmotic  pressure  of  haemoglobin, 
90 

Osmotic  pressure  of  gelatine,  90 

Osmotic  pressure,  determination 
of,  with  red  blood  cells,  55 

Osmotic  pressure,  effect  of  tem- 
perature on,  50 

Osmotic  pressure,  effect  of  con- 
centration of  solution  on,  51 

Osone,  236 

Oxalates,  196 

Oxalic  acid,  195 

Oxaluric  acid,  287 

Oxamide,  276 

Oxycamphor,  313 

Oxygen,  calculation  of  percent- 
age of,  38 

Oxyproteic  acid,  298 

Oxyquinoline  sulphate,  421 

Palmitic  acid,  187,  303 
Palmitin,  203 
Palmito-distearin,  204 
Papaverine,  435 
Paper,  246 
Parabanic  acid,  287 
Para  compounds,  326 
Paradihydroxybenzene,  346 
Paraffin,  122 

"        derivatives,  107 
oil,  122 

"        series,  117 
Paraffins,  104,  117 

"  ,  boiling-points,  spe- 
cific gravities,  etc., 
120 

"  ,  heat  of  combustion 
of,  121 

"       ,  synthesis  of,  117 
Paraformaldehyde,  148 


INDEX 


467 


Parahydroxymetamethoxyallyl- 

benzene,  347 
Parahydroxytolyl    mustard    oil, 

343 

Paraldehyde,  151 
Paraminophenol,  382 
Paraminosulphonic  acid,  394 
Paraphenetidin,  382 
Pararosaniline,  379 
Paratoluic  acid,  362 
Parchment  paper,  246 
Pelletierine,  425 
Pentane,  120,  123 
Pentoses,  229 
Pentose  test,  230 
Peppermint,  oil  of,  313 
Peptides,  296 
Peptone,  297 

Percentage   composition,   calcu- 
lated from  analysis,  34 
Peronine,  439 
Petroleum,  121 

ether,  121 

ether,  specific  grav- 
ity of,  25 
Phenacetin,  382 
Phenanthrene,  413 
Phenazone,  415 
Phendiol,  345 
Phenetole,  340,  385 
Phenocoll,  383 
Phenol,  336,  337,  385,  392 
Phenol,  derivatives  of,  340 
"      ,  substitution       products 

of,  341 

Phenolates,  336 
Phenolic  acids,  363 
Phenolphthalein,  372,  399,  402 
"  ,  tautomerism 

of,  402 

Phenol-sulphonic  acids,  342,  393 
Phenols,  336 

11      ,  diacid,  337,  345 
"      ,  monacid,  337 
"      ,  triacid,  337,  348 
Phenoxides,  336 


Phentriol,  348 
Phenyl,  329 
Phenylacetamide,  381 
Phenyl  acetate,  341 

1 '      acetic  acid,  362 

"      alanin,  269,  371 

"      amine,  376 

11      carbinol,  349 
Phenylethyl  ether,  340 
Phenylhydrazine,  148,  235,  352, 

388 

Phenylmethyl  ether,  340 
Phenylpropionic  acid,  362 
Phenyl  salicylate,  365 
Phenyltolylketone,  354 
Phloretin,  252 
Phloridzin,  252 
Phloroglucin,  348 
Phloroglucinol,  348 
Phloroglucin-vanillin       reagent, 

348,  402 
Phosgene,  128 
Phosphatides,  262 
Phosphine,  substitution  deriva- 
tives, of,  264 

Phosphorus-containing         com- 
pounds, 262 
' '          ,  detection  of,  5 
Phthalic  acid,  330,  371 

"        anhydride,  371 
Phthalimide,  372 
Physical     properties     of     sub- 
stances, 22 
Physostigmine,  426 
Phytosterol,  315 
Picnometer,  23 
Picric  acid,  341 
Picropodophyllin,  442 
Picrotoxin,  442 
Pilocarpidine,  426 
Pilocarpine,  441 
Pinene,  311 

"      hydrochloride,  311 
Pine  oils,  311 
Pintsch  gas,  119 
Piperazine,  264 


468 


INDEX 


Piperidine,  428 
Pipeline,  428 
Plasmolysis,  57 
Polarization,  245 
Polymerization,  148,  151 
Polymers,  148 
Polymethylenes,  310 
Polypeptides,  296 
Polysaccharides,  228,  246 
Polyterpenes,  314 
Potassium  acetate,  165 

acid  tartrate,  224 
antimonyl     tartrate, 

225 
benzene    sulphonate, 

337,  357,  393 
hydroxide,       specific 
gravity  table,  449 
phenol  sulphate,  340 
Pressure,  osmotic,  46 
' '       ,  vapor,  450 
Primary  alcohols,  110,  136 

"       amines,  257 
Prolin,  271,  415 
Propane,  105,  120 
Propene,  302 
Propenol,  302 
Propionic  acid,  184 
Propyl  alcohol,  144 

' '       ' '        ,  secondary,  189 
Propylene,  201 
a-Propyl  piperidine,  429 
Protamines,  271 
Protein,   formation  of  dextrose 

from,  233 

1 '       ,  synthesis  of,  296 
Proteins,  classes  of,  298 
Protocatechuic  acid,  368 
Prussic  acid,   see    Hydrocyanic 

acid. 

Pseudo-catalyst,  180 
Ptomaines,  263 
Purification  of  substances,  7 
Purin  bodies,  292 
"     nucelus,  292 
Purpuric  acid,  291 


Putrescine,  263 
Pyoktanin,  380 
Pyramidon,  415 
Pyrazole,  414 
Pyridine,  416 

bases,  415 

Pyrimidin  derivatives,  294 
Pyrimidin  ring,  287 
Pyrocatechin,  345 
Pyrocatechol,  345 
Pyrogallic  acid,  348 
Pyrogallol,  348 
Pyroligneous  acid,  162 
Pyroxylin,  247 
Pyrrol,  414 
Pyrrolidine,  415 
a-Pyrrolidine-carboxylic       acid, 

271 

Pyrrolidine  derivatives,  430 
Pyruvic  acid,  140,  192 

Quantitative  analysis,  28,  40 
Quaternary  bases,  114,  260 
Quinalgen,  422 
Quinidine,  434 
Quinine,  420,  434 

"      bisulphate,  440 
Quinine-urea  hydrochloride,  434 
Quinoid  structure,  402 
Quinol,  346 
Quinoline,  420 
Quinones,  398 

Racemic  lactic  acid,  217 
"  substances,  216 
' '  tartaric  acid,  223 

Reduction  tests,  235 

Reichert-Meissl  value,  205,  207 

Resorcin,  346 

Resorcinol,  346 

Reversible  reactions,  175 

Rhamnose,  230 

Rhein,  413 

Rhigoline,  121 

Ricinoleic  acid,  304 


INDEX 


469 


Rochelle  salt,  225 

Rosaniline,  379 

Rotation     of     polarized     light, 

216 
Rotatory  power  of  sugars,  236, 

245 
Rubber,  314 

Saccharates,  244 
Saccharic  acid,  232 
Saccharin,  394 
Saccharose,  241,  243 
Safrol,  347 
Sajodin,  188 
Salicin,  252 
Salicylic  acid,  363 

combustion    anal- 
ysis of,  32 

Salicyl-sulphonic  acid,  393 
Saligenin,  252,  351 
Salipyrin,  367 
Salol,  365 
Salophen,  366 
Salvarsan,  396 
Sandalwood  oil,  314 
Sanguinarine,  426 
Sanoform,  366 
Santonin,  410 
Santoninic  acid,  410 
Saponification,  208 

value,  205 
Saponin,  253 
Sarcolactic  acid,  217 
Sarcosin,  268 
Sassafras  oil,  366 
Saturated    hydrocarbons,     103, 

117 

Schiff's  reagent,  154 
Schweitzer's  reagent,  246 
Scopolamine,  432 
Scopolin,  432 
Secondary  alcohols,  110,  189 

' '         amines,  258 
Selective  permeability,  57 
Semipermeable  membrane,  47 
Serin,  268 


Side  chain,  106,  356 
Sidonal,  264 
Silk,  artificial,  248 

"  ,  viscose,  248 
Sinalbin,  253 
Sinigrin,  253 
Sinipine,  426 

"  Six  hundred  and  six,"  396 
Skatol,  417 

Skatoxylsulphuric  acid,  418 
Smokeless  powder,  248 
Soap,  castile,  209 
'     ,  cleansing  action  of,  209 
'     ,  green,  209 
'     ,  hard,  209 
'    ,  resin,  209 
'     ,  soft,  209 
1    ,  Venetian,  209 
Soaps,  209 
Sodium  acetate,  165 
"       amalgam,  220 
' '       hydroxide,  specific  grav- 
ity table,  448 
"       methyl,  131 
"       methylate,  137 
"       oleate,  209 
"      phenylcarbonate,  363 
' '       potassium  tartrate,  225 
' '       salicylate,  364 
Solute,  47 
Solutions,  47,  59 

11        ,  colloidal,  81 
"        ,  electrical     conductiv- 
ity of,  65 
"        ,  isotonic,      hypotonic, 

hypertonic,  55 
1 1        ,  obedience  to  gas  laws, 

50 

Solvents,  7 
Sorbitol,  232 
Sparteine,  427,  430 
Spatial  representation  of  mole- 
cules, 215 
Specific  gravity  determination, 

23 
"       "         of  liquids,  23 


470 


INDEX 


Specific  gravity  of  solids,  24 

"       "'       tables,    445, 

448,  449,  450 
Spermine,  264 
Starch,  249 

' '     ,  soluble,  88 
Steam  distillation,  16 
Stearic  acid,  187,  303 
Stearin,  203 

Stereochemical  isomerism,  214 
Stereoisomerism,  214 
Sterins,  315 
Stovaine,  360 
Strophanthin,  253 
Structural  formula,  98 
Structural    formula    of    acetic 

acid,  proof  of,  164 
Strychnine,  435 
Stypticin,  437 
Sublimation,  13 
Submicrons,  87 
Substituted  ammonias: 

Primary,  257 

Secondary,  258 

Tertiary,  258 
Succinic  acid,  197 
Succinic  anhydride,  198 
Succinimide,  284 
Sucrose,  241,  243 
Sugars;     comparative    reducing 
power  of,  241 

' '      ,  estimation  of,  241 

1 '     ,  specific  rotation  of,  245 

' '     ,  tests  of,  239 
Sulphanilic  acid,  394 
Sulphobenzoic  acids,  360 
Sulphocyanic  acid,  257 
Sulphonal,  307 
Sulphones,  306 
Sulphonic  acids,  115,  306 

"       ,  aromatic,  391 
"         chlorides,  391 
Sulphonmethane,  307 
Sulphur  alcohols,  115,  306 

' '       -containing  amino  acids, 
272 


Sulphur,  derivatives  of  paraffins, 
115,  306 

' '       ,  detection  of,  3 

11       ethers,  115,  306 
Suprarenin,  384 
Surface  tension,  71,  88 
Suspensoids,  81 
Synthesis,  6 


Tannacol,  370 
Tannalbin,  370 
Tannic  acid,  88,  368 
Tannigen,  370 
Tannins,  370 
Tannoform,  370 
Tartar  emetic,  225 
Tartaric  acids,  222 
Tartronic  acid,  202,  221,  290 
Taurin,  272 
Taurocholic  acid,  221 
Tautomerism,  290,  401 
Terpenes,  310 
Terpin,  312 
Terpin  hydrate,  312 
Tertiary  alcohols,  110,  192 
"        amines,  258 

bases,  114,  425 
Tetrabromfluorescein,  373 
Tetrachlormethane,  120,  127 
Tetrathylamrnonium       hydrox- 
ide, 260 

Tetra-iodo-methane,  131 
Tetra-iodo-pyrrol,  414 
•  Tetramethoxybenzylisoquino- 

line,  435 
Tetranitrol,  202 
Tetraphenylhydrazine,  381 
Tetronal,  307 
Tetrose,  229 
Thalline,  422 
Thebaine,  439 
Theobromine,  294,  441 
Theophylline,  441 
Thio  alcohols,  306 
Thiophene,  319,  414 


INDEX 


471 


Thiophenol,  391 
Thiosinamine,  308 
Thyme,  oil  of,  332,  344 
Thymin,  295 
Thymol,  343 
Toluene,  329 

Toluene-sulphonic  acids,  391, 393 
Toluic  acids,  362 
Toluidines,  378 
Toluol,  329 
Tolyl  carbinol,  351 
Tragacanth,  gum,  251 
Traube's  synthesis,  287 
Tribrommethane,  127 
Tribromphenol,  341 
Trichloracetic  acid,  170 
Trichloraldehyde,  154 
Trichlorhydrin,  200 
Trichlorlactamide,  289 
Trichlormethane,  120,  127 
Trichlortertiary   butyl    alcohol, 

191 

Tricresol,  343 
Trihydroxybenzene,  348 
Trihydroxybenzoic  acid,  368 
Triiodoacetone,  191 
Triiodomethane,  129 
Trimethylamine,  261 
Trimethylene,  310 
Trinitrobenzene,  326 
Trinitrocellulose,  248 
Trinitro phenol,  341 
Trinitrotoluene,  376 
Trional,  307 
Trioses,  228 
Triphenylamine,  380 
Triphenylmethane  dyes,  380 
Trisaccharides,  228,  246 
Tropacocaine,  433 
Tropaeolin  OO,  396 
Tropic  acid,  431 
Tropine,  431 

Tryptophan,  220,  271,  418 
Turpentine,  311 
Tussol,  415 
Tyrosin,  269,  371 


Ultrafiltration  of  colloids,  86 
Ultramicroscope;  87 
Unsaturated  hydrocarbons,  103 
Uracil,  295 
Urates,  291 
Urea,  277 

' '  ,  freezing-point  determina- 
tion of  molecular  weight. 
62 

"    ,  nitrate,  281 

"    ,  oxalate,  281 

' '    ,  specific  gravity  of,  25 

"    ,  synthesis  of ,  1,278,281 
Urethane,  267 
Uric  acid,  286,  293 

' '        ,  tautomerism  of,  290 
Urine,    depression    of    freezing- 
point  of,  64 
Urinometer,  24 
Urotropine,  264 

Vacuum  distillation,  16 
Valence  of  elements  in  organic 

compounds,  2 
Valerianic  acid,  187 
Valeric  acid,  187 
Valin,  269 
'Vanilla,  368 
VaniUic  acid,  368 
VaniUin,  368 

Vapors,  molecular  weight  of,  41 
Vapor  tension  table,  450 
Vaseline,  122 

Vegetable  bases,  see  Alkaloids. 
Veratrine,  427 
Veronal,  282 
Victor    Meyer's    vapor   density 

method,  44 
Vinegar,  162 
Viscosity,  77 

' '          of  colloidal  solutions, 

89 

number,  79,  207 
Von  Baeyer's  reagent,  301 

Water-gas,  119 


472 


INDEX 


Waxes,  192 

Weight  normal  solutions,  50 
Westphal's  balance,  23 
Whiskey,  140 
Wines,  140 

Wintergreen,  oil  of,  365 
Wood  alcohol,  138 
"      turpentine,  311 

Xanthin,  293 

"       bodies,  293 


Xylene,  meta,  330,  331 
Xylenes,  330 
Xylidines,  378 
Xylol,  330 
Xylose,  229,  233 

Yeast,  fermentation  by,  141 
Yohimbine,  426 

Zinc  methyl,  131 
Zymase,  141 


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